By the early 1990s only 90 individuals of the endangered Arctic fox subspecies Alopex lagopus semenovi, remained. These few survivors are confined to Mednyi Island, part of the Commander Islands chain. The formerly abundant population crashed in the mid-1970s and has never recovered from only 10–15 per cent of its former numbers. In 1983 the Mednyi Island foxes were listed in the Russian Red Data Book. Their demise coincided with the arrival of mange, introduced by seafaring trappers and caused by the mite Otodectes cynotis, which was associated with devastating cub mortality. In 1994, in a unique intervention, we sought to save the population by treating cubs with antiparasitic drugs. That summer, mortality was reduced. A census in 1995 suggested that over-winter survival was at least no worse, although it is too soon to judge whether this intervention can be a route to population recovery.