It was hypothesized that the manner in which attitudes influence behaviour is moderated by the level of effort required to perform a behaviour. The effort needed was manipulated in a field experiment by varying the difficulty of getting access to the attitude object. When the behaviour required substantial effort, the mediating role of intentions was strong, and attitudes had only indirect effects on behaviour, consistent with the theory of reasoned action. When the behaviour required little effort, however, attitudes had a significant direct effect on behaviour, and the mediating role of intentions was reduced. The theoretical and practical implications of these findings are discussed.