We study consumers’ motivations for buying organic food by analyzing their shopping baskets. Buying organic can be motivated by concern about sustainable development and/or self-interest (considerations related to health or product quality). Pro-social motivation is inferred from the presence of fair trade products in the consumer's basket; consumer self-interest is deduced from the presence of healthy and higher-quality products bearing special quality labels or certifications. Our results indicate that environmental motivation predicts organic food purchases better than health or quality considerations: the complementarity between organic and fair trade products is strongest. In addition, the household's socioeconomic background influences secondary motivations.