Previous studies evaluating short-term itraconazole and terbinafine therapy for onychomycosis have varied in protocol and size; this double-blind study enabled a large-scale, standardized, direct comparison. Patients with toenail onychomycosis were randomized to itraconazole 200 mg daily (n = 146) or terbinafine 250 mg daily (n = 146) for 12 weeks, with a 36-week follow-up. Mycological cure rates at the follow-up end-point were significantly equivalent (61% with itraconazole vs. 67% with terbinafine). A similar proportion of patients in each group experienced adverse events during treatment (itraconazole, 22%; terbinafine, 23%). More patients receiving terbinafine stopped treatment permanently because of treatment-related adverse events (8% vs. 1%).