The relevance of associative learning in the development of Obsessive-Compulsive Disorder (OCD) was investigated in a group of 23 OCD patients whose main concern was washing and 23 age and sex matched control subjects who did not have OCD. OC washers completed an origins instrument based on Menzies and Clarke's (1993, Behaviour Research and Therapy, 31, 355-365) Origins Questionnaire (OQ) for the phobic disorders. Control subjects completed a modified version of this measure designed to give a comprehensive picture of their experiences with relevant contamination-related stimuli. In general, the results question the relevance of associative-learning per se in the development of OC washing. Direct and indirect conditioning events were very rare in the OCD group, accounting for less than 13% of cases. No significant differences between groups were found in the proportion of subjects who knew other OC washers, or had experienced direct associative-learning events prior to onset. Contrary to expectation, significantly more non-OCD subjects had experienced vicarious learning events related to dirt and washing than OCD subjects. However, of note, associative-learning events that took place during episodes of depression were significantly more frequently reported in the OCD group than in the control group. Depression appeared to play a facilitating role in the associative-learning of OC washing. The implications of these findings for theoretical accounts of OCD are discussed.