At present the reported use of itraconazole, a new oral triazole antifungal, has been confined to short-term treatments. This investigation is an appraisal of itraconazole in the treatment of three different forms of onychomycosis. Six patients with nail infections due to Candida albicans not associated with paronychia affecting a total of 20 nails received itraconazole (100 mg daily) for a mean period of 5.9 months. Complete remission was achieved in all cases. Twenty six patients with dermatophyte onychomycosis affecting a total of 45 finger and 80 toe-nails were treated with itraconazole (100-200 mg daily). In 24 cases the causative organism was Trichophyton rubrum. Remission was achieved in 64% of finger and 73% of toe-nails in 5 and 9.4 months, respectively. Treatment failures were experienced in patients with finger-nail infections due to T. violaceum (I) and those concurrently receiving phenytoin and phenobarbitone (3). Three patients with infections due to Hendersonula toruloidea failed to respond to treatment. Adverse effects were experienced by four patients (abdominal discomfort 3, diarrhoea I), but none were serious enough to lead to abandonment of treatment. No persistent changes were seen in serum biochemical values. This study suggests that itraconazole is potentially effective in the long-term treatment of superficial fungal infections such as onychomycosis, and comparative studies with alternatives such as griseofulvin should now be carried out.