To see which foam or feather-filled topper might improve a too-hard bed, we tested seven. Five use “memory foam,” a polyurethane material that conforms to your body. They’re 1 to 3 inches thick and cost $70 to $890 in queen size--as much as some mattresses. The others are filled with feathers and down. They’re about 5 inches thick and cost $130 and $150.

Six couples with firm mattresses slept on each topper for up to a week at a time and filled out a questionnaire.

What we found. For many toppers, opinions varied. A few firm conclusions:

• Price was no harbinger of a good night’s sleep. One panelist said lying on the Tempur-Pedic memory foam, $890, was like sinking in quicksand.
• Neither of the featherbeds tickled the fancy of most panelists. Some said the toppers shifted overnight and made beds look lumpy.
• Odor can be an issue. Panelists noted that some foam toppers had a rubber or chemical scent even after they were aired out for a day or two. Our tests for emissions suggest that it makes sense to air out a new foam topper.

CR's take. Spa Sensations, $70, was panelists’ favorite, but no one topper is best for everyone. Check the return policy: Unlike mattresses, toppers can’t be tried in the store. Bed Bath & Beyond and L.L.Bean told us returns are allowed; other stores didn’t respond to requests for return info. (In any case, foam toppers are unwieldy once expanded.) Before you shop, consider whether your sheets will fit mattress plus topper.