This open-label multicenter study evaluated the safety and efficacy of 12, 18, and 24 weeks of daily treatment with a 250-mg tablet of terbinafine for onychomycosis of the toenails. The safety data for 1,508 patients with a mean age of 50 years are reported here. Percentages below are based on this denominator. All patients received at least 12 weeks of therapy, with a possible addition of 6 or 12 weeks depending on disease extent. Patients were evaluated at baseline and at weeks 6, 12, 24, 30, 36, 48, and 72. Adverse events were reported in 674 (44.7%) patients; the events were considered unrelated to terbinafine in 557 (36.9%) patients and causally related or of uncertain relationship to terbinafine in 117 (7.8%) patients. Most events involved the skin, the gastrointestinal system, or the respiratory system. Statistically similar results were found for the elderly (over 60 years) and diabetic subpopulations. The study results confirm the safety of terbinafine in the population at large and show no differences for either the elderly or diabetic patients, who are at increased risk for onychomycosis and who frequently take concomitant medications with potential for drug interactions.