The objective of this paper is twofold. First, the authors aim to analyse the factors that affect the intention of Czech consumers to purchase organic food using the theory of planned behaviour (TPB). Second, they employ an extended TPB model that introduces descriptive norms as an additional actor of behavioural intention. This study exploits data from a consumer survey of a sample of the Czech general adult population (N = 252) conducted in 2010. Structural equation modelling with an ML estimator is used to estimate model parameters. The empirical model derived from the TPB explains 44% of the variability of intention to purchase organic food. Descriptive norms are empirically distinct from injunctive norms and their inclusion in the model increases the explained variance of intention by an additional 5 percentage points. Attitudes and norms are the strongest predictors of the intention to purchase organic food, while perceived behavioural control has only a weak effect.