Objective: Efficacy and safety of sequential pulse therapy with itraconazole and terbinafine were compared with pulse terbinafine alone in the treatment of toenail onychomycosis. Methods: This was a 72-week prospective, single-blind, randomized, multicenter, comparative, parallel group, nonindustry-sponsored trial. A total of 190 patients were recruited from 3 outpatient dermatology offices in North America. Patients were at least 18 years old and had a clinical and mycologic diagnosis of dermatophyte toenail onychomycosis. Patients were randomly assigned to receive sequential pulse therapy (IIT) with 2 pulses of itraconazole followed by 1 or 2 pulses of terbinafine (itraconazole pulse is 200 mg twice daily for 1 week and terbinafine pulse is 250 mg twice daily for 1 week) versus 3 or 4 pulses of terbinafine (TTT). Main outcome measures at week 72 evaluated mycologic cure rate (negative light microscopy and culture), clinical cure (nail appears completely or totally normal), complete cure (clinical and mycologic cure), and effective therapy (mycologic cure and clinical response with at least 5 mm of new, uninvolved nail growth). Results: At week 72, in the IIT versus TTT groups, the mycologic cure rate was 54 of 75 (72.0%) versus 44 of 90 (48.9%), clinical cure rate was 42 of 75 (56.0%) versus 35 of 90 (38.9%), effective therapy 49 of 75 (65.3%) versus 41 of 90 (45.6%), and complete cure 39 of 75 (52.0%) versus 29 of 90 (32.2%), respectively. Both regimens were well tolerated with no new adverse effects being identified. The rate of permanent discontinuation of therapy because of adverse effects was 2 of 81 (2.5%) with IIT and 2 of 95 (2.1%) with TTT. Each of the adverse effects normalized over time. The number of patients who reported an adverse effect in the 2 groups was 12 of 81 (14.8%) versus 22 of 95 (23.2%), respectively. All these adverse effects were reversible and mild to moderate in severity. Conclusion: Sequential pulse therapy with itraconazole and terbinafine is effective and safe for the treatment of dermatophyte toenail onychomycosis. (J Am Acad Dermatol 2001;44:485-91.)