Predation on endangered species by nonnative red foxes (Vulpes vulpes) and the resulting controversy over red fox control efforts in California prompted our investigation of the introduction and range expansion of the red fox in California. Since the late-1800s, nonnative red foxes have been introduced into California by escaping from fur farms and fox hunters, through intentional releases by pet owners and fur-farm owners and translocations of previously introduced foxes. From 1990–1993 we conducted telephone interviews of wildlife professionals to obtain observations of nonnative red foxes outside the historical range of the native Sierra Nevada red fox (V. v. necator). Nonnative red foxes now occur throughout lowland areas of California including the Sacramento and San Joaquin valleys, San Francisco Bay-Delta area, the southern California Coast Range and Coastal Plain and most major urban areas. Their range expansion over the last 100 y was the result of population growth from numerous points of introduction and exhibited by the exponential growth typical of invading species. Fox predation on endangered species and opposition to red fox management have been the two largest management issues associated with this range expansion.