Otitis externa (OE) and especially otomycosis can be very persistent and difficult to control. In the present study the efficacy of treatment of OE with a single instillation in the ear canal of one per cent silver nitrate in three per cent hypromellose gel compared to 0.1 per cent silver nitrate gel was tested in a single-blinded randomized controlled parallel group study. The outcome measure was complete resolution of the OE after one week. Forty-four patients with refractory, bacterial as well as fungal, OE entered the study, comprising 30 ears in each treatment arm. Eight patients defaulted from follow-up,five ears in each treatment arm. A single instillation of one per cent silver nitrate gel cured 23 (92 per cent) of 25 ears with OE, whereas with 0.1 per cent silver nitrate gel seven (28 per cent) of 25 ears treated were cured (Fisher-exact test, p-exact = 0.00010). In a non-controlled series of 120 ears 93.3 per cent needed only a single instillation of one per cent silver nitrate gel while another five per cent were cured after a second instillation a week later. There were no adverse reactions. OE can be treated effectively with instillation of one per cent silver nitrate gel and is particularly useful in recalcitrant otomycosis. The treatment method saves both cost and time.