Pedometers have been identified as a tool for health professionals to promote physical activity. This study, which aimed to evaluate the effectiveness of wearing a pedometer on general practitioners' attitudes to promoting physical activity, was a pragmatic, multi-centred, randomized controlled trial within a primary care trust in England. The participants were 102 general practitioners (GPs). Eighty-five (48 males, 37 females) of the GPs completed pre and post questionnaires, 43 of whom were in the intervention group. Statistical analysis revealed no significant changes between the control and intervention groups for attitude to engage in physical activity (t(83) = 1.13, CI -0.362 to 0.099) or attitude to promote physical activity in their patients (t(83) = 1.7, CI -0.593 to 0.045). A higher volume of walking was significantly correlated with a more positive attitude to engage in physical activity (r = 0.58, P < 0.01) but not with a more positive attitude to promoting physical activity. Wearing a pedometer had no significant effect on GPs' attitudes to engaging in physical activity or promoting physical activity in their patients.