The safety of naproxen sodium for over-the-counter use was evaluated based on 48 randomized, double-blind, placebo-controlled clinical trials that evaluated naproxen/naproxen sodium (NAP) for indications appropriate to, and under, conditions common to, nonprescription analgesics. Of the 48 studies, 27 were single-dose studies and 21 were multiple-dose studies of 1 to 10 days' duration; 19 studies included ibuprofen and 9 included acetaminophen. A total of 4138 patients received naproxen or naproxen sodium (3589 patients received naproxen 187.5 to 400 mg and 549 received naproxen sodium 220 to 440 mg), 2423 received placebo, 1574 received ibuprofen (200 or 400 mg), and 671 received acetaminophen (500 to 1000 mg). Adverse-event rates were examined in three sets of comparisons: NAP versus placebo (48 studies); NAP versus ibuprofen and placebo (19 studies); and NAP versus acetaminophen and placebo (9 studies). Across all 48 studies, 83% of both the NAP- and placebo-treated patients reported no adverse events. The incidence rates were similar between NAP and placebo, with headache (4.8% NAP, 6.4% placebo), nausea (3.4% NAP, 3.1% placebo), and somnolence (2.7% NAP, 1.9% placebo) the most commonly reported events. Rates of adverse events with NAP, ibuprofen, and acetaminophen were similar.