Consumer Reports: All but one of the products we tested met their label claims for key essential vitamins and minerals, and none contained worrisome levels of contaminants such as arsenic or heavy metals. Most of the pills we tested also passed the U.S. Pharmacopeia's dissolution test, which involves immersing them in a simulated stomach-acid solution to determine whether they'll dissolve properly in your body. (The USP is an independent standards-setting authority for the drug and dietary supplement industries.)
What's more, they found that store brands did just as well in our tests as national brands, at a lower price. The biggest winner: Costco's Kirkland Signature, whose regular, "mature," and children's multis cost a nickel or less a day.