Combination therapy is one way of improving the cure rate of onychomycosis. The LION Study examined the efficacies of terbinafine and itraconazole. The Icelandic cohort of the study reported that after 5 years only 46% of the terbinafine-treated patients and 13% of the itraconazole-treated patients were still disease-free, suggesting that relapses and reinfections were common in the long term treatment of onychomycosis with monotherapy. Combination therapy is a well-established principle in mycology; the current strategy involves the combination of oral and topical antifungal treatments. A number of specific drug combinations have proved to be useful in the treatment of onychomycosis: tioconazole and griseofulvin, amorolfine and griseofulvin, amorolfine and terbinafine, and amorolfine and itraconazole. However, comparison of the combination trials can be difficult because of the short duration of some of the studies and variation in global cure rates. Although it is necessary to consider these factors it is clear that combination therapy offers advantages when compared with monotherapy. Combination therapy can be administered sequentially or in parallel. Parallel therapy is recommended for patients who are likely to fail therapy (e.g. patients with diabetes), whereas sequential therapy is recommended for patients who show a poor response to initial treatment.