After languishing for decades, those boxes of baseball cards gathering dust in your closet could be valuable. Overproduction in the 1980s and 1990s undercut prices and soured a generation of collectors on the hobby, but free time and disposable income have inspired collectors to look for the cards they had as children. The past two years have brought a rally, with certain cards selling for two-to-10 times or more what they would have brought as recently as 2018. Example: Ken Griffey, Jr.’s 1989 Upper Deck rookie card consistently sold for $20 to $40 for decades. Now it routinely brings $100*, with mint-condition examples reaching $400 to $500 and examples in “pristine” condition, which is very rare, reaching as high as $2,000.

This might be the start of a long-term recovery for sports cards…but there’s also reason to worry that the bubble will deflate or burst in the months or years ahead. Many of today’s buyers are new to the hobby and seem motivated by financial speculation. And the increased attention to online sports card auctions might be because people have been stuck home during the pandemic.

Here’s what you need to know to bring your cards to the trading table…

Look to the Stars

The recent rebound has not benefited all players’ sports cards evenly. The values of cards featuring top stars have shot up—especially those stars’ “rookie cards”—while cards featuring lesser players continue to be worth little or nothing. Example: That Ken Griffey, Jr., rookie card mentioned earlier is part of an 800-card set. The entire set sells for virtually the same price as the combined value of its three most valuable cards—the rookie cards of stars Griffey, Randy Johnson and Gary Sheffield. The combined value of the other 797 cards is negligible.

Examples of the rapidly rising values of stars’ cards…

Mickey Mantle 1961 Topps. ­Mantle’s 1952 Topps card is famously valuable—one in especially nice condition recently sold for a staggering $5.2 million. But the recent rally has dramatically increased the value of cards from later in Mantle’s career, too. A Mantle card in near-mint condition—meaning that it showed few or no signs of wear—from the 1961 Topps set could have been had for $150 to $200 a few years ago but now could bring around $700 to $1,500.

Rickey Henderson 1980 Topps. Hall-of-Famer Henderson’s rookie card sold for $40 to $50 for many years, but now it brings $100 to $120 in near-mint condition. One in nearly perfect condition recently sold for $55,000.

Cal Ripken, Jr., 1982 Topps ­Traded. This card was part of a special “Traded” set that Topps released after its primary 1982 baseball card set. For years, it sold for $10 or $12, but it now brings $100 or more in near-mint condition and as much as $1,000 in flawless condition.

Unopened boxes and packs of cards from decades past also can bring big bucks these days—buyers are gambling that these might contain mint-­condition cards of stars.

It Isn’t Just Baseball

Baseball cards have historically dominated the sports card market, but cards featuring basketball and football stars have surged in value as well. In fact, this recent rally began with basketball cards—the recent rookie cards of young talents Luka Doncic, Ja Morant, Zion Williamson and Trae Young attracted new collectors. Valuable basketball and football cards include…

Oscar Robertson 1961 Fleer basketball. Cards featuring Hall-of-Fame basketball players from the 1960s and early 1970s have been especially hot lately. This card featuring the legendary 12-time All-Star Robertson previously sold for $100 to $200 but now routinely brings $2,000 to $3,500. One in near-mint condition recently fetched $14,800.

Jerry Rice 1986 Topps football. This Hall-of-Fame wide receiver’s rookie card previously sold for $15 to $30 but now brings around $350 to $400…or as much as $1,600 in mint condition.

1994 Bumble Bee Dwayne Johnson. In 1994, Bumble Bee Tuna released a set of cards featuring members of the University of Miami football team as a special promotion. Included in the set was a card featuring a defensive tackle named Dwayne Johnson—he would later achieve fame as wrestler-turned-actor “The Rock.” A few years ago, you could have bought this card for just $2 or $3, but now they’re selling for $2,000 and up, depending on condition. One sold last year for $79,200.

How to Sell Your Cards

The easiest way to determine the value of your cards is with eBay. The prices that matter are the amounts the cards actually have sold for on eBay, not the amounts sellers ask. To find these actual sale prices on eBay, click the word ­“Advanced,” which appears next to the eBay search button, then click the “sold listings” box and enter relevant keywords—such as year, set and name. Example: “2017 Panini Prizm Patrick Mahomes.” Remember that the condition of your card will have a massive effect on its value—the fact that a card in pristine condition sold for $1,000 doesn’t mean that your creased version of the same card has any significant value.

If you have cards that sell for hundreds of dollars or more on eBay, e-mail the details to one or more of the respected auction houses that handle sports cards to see if they’re interested in selling them—Collect Auctions ­(CollectAuctions.net)…Goldin Auctions (GoldinAuctions.com)…and/or Heritage Auctions (HA.com). Most auction houses take a commission on the sale as well as charging the buyer a premium. Cards generally fetch higher prices when sold through these auction houses than by individuals on eBay, though selling on eBay is the best fall-back option if the auction houses aren’t interested.

To get top dollar, you must have your cards professionally graded by Beckett Grading Services or sports card grader PSA (PSACard.com). ­Example: A 1961 Topps Mickey Mantle sells for around $700 with a condition grade of seven…while the same card in comparable condition but without a grade from one of these services brings around $450—buyers consider ­ungraded cards more risky.

Grading isn’t cheap, so it is worthwhile only with cards likely to sell for well into three figures or higher. The cost for grading varies but can be around $50 per card for standard grading services such as at PSA and Beckett. Expedited service can cost $150 or more per card but might be worthwhile in this market—the pandemic and sports card rally have combined to push wait times for non-expedited services out past six months.

If you wish to sell all of your cards, not just the valuable stars, contact local sports card shops to see if they’re interested in buying your less valuable cards in bulk…or contact Burbank Sportscards ­(BurbankCards.com), which, unlike most major sports card dealers, does purchase lower-value cards. But expect their offers to be pennies per card at most.