BACKGROUND: Features of the local fast food environment have been hypothesized to contribute to the greater prevalence of obesity in deprived neighborhoods. However, few studies have investigated whether fast food outlets are more likely to be found in poorer areas, and those that have are local case studies. In this paper, using national-level data, we examine the association between neighborhood deprivation and the density of McDonald's restaurants in small census areas (neighborhoods) in Scotland and England. METHODS: Data on population, deprivation, and the location of McDonald's Restaurants were obtained for 38,987 small areas in Scotland and England (6505 "data zones" in Scotland, and 32,482 "super output areas" in England) in January 2005. Measures of McDonald's restaurants per 1000 people for each area were calculated, and areas were divided into quintiles of deprivation. Associations between neighborhood deprivation and outlet density were examined during February 2005, using one-way analysis of variance in Scotland, England, and both countries combined. RESULTS: Statistically significant positive associations were found between neighborhood deprivation and the mean number of McDonald's outlets per 1000 people for Scotland (p<0.001), England (p<0.001), and both countries combined (p<0.001). These associations were broadly linear with greater mean numbers of outlets per 1000 people occurring as deprivation levels increased. CONCLUSIONS: Observed associations between presence or absence of fast food outlets and neighborhood deprivation may provide support for environmental explanations for the higher prevalence of obesity in poor neighborhoods.