Professional tooth whitening in a dentist's office can brighten your smile in as little as one visit, but it can cost hundreds of dollars. Over-the-counter home whitening kits cost far less, and there's an ever-expanding array of options—including strips that dissolve, strips that stick on, and even light-activated trays.

How well do they whiten? We tested eight products that cost from $17 to $50 and found a clear winner.

Each of the 82 staffers in our test panel was given a product and asked to use it as directed for the number of days recommended by the manufacturer (from five days to three weeks). We used a digital color-measuring device to assess staffers' tooth color before and after the course of whitening. The testers also described their experiences with the product. The Ratings (for subscribers) are based mainly on whitening scores.