Qualitative research and cross-sectional survey methods were used in a study conducted in rural and urban areas of the Greater Accra Region, Ghana, to explore people's understanding of the cause of malaria and patterns of mosquito avoidance, in particular bed net ownership and use. The study indicated far higher bed net ownership and use in rural than urban areas, which was related partly to perceived affordability and partly to the different contexts of and reasons for avoiding mosquitoes. Knowledge of an association between mosquitoes and malaria, the most common cause of illness in both areas, was related to residence but not to literacy or formal education, and this knowledge did not predict bed net use. The paper points to the complexity of social and personal factors implicated in behavioural interventions for malaria control, and questions behavioural models that assume a linear relationship between knowledge and practice.