If human beings care about their relative weight, a form of imitative obesity can emerge (in which people subconsciously keep up with the weight of the Joneses). Using Eurobarometer data on 29 countries, this paper provides cross-sectional evidence that overweight perceptions and dieting are influenced by a person's relative BMI, and longitudinal evidence from the German Socioeconomic Panel that well-being is influenced by relative BMI. Highly educated people see themselves as fatter-at any given actual weight-than those with low education. These results should be treated cautiously, and fixed-effects estimates are not always well determined, but there are grounds to take seriously the possibility of socially contagious obesity. (JEL: D1, I12, I31) (c) 2009 by the European Economic Association.