This paper examines behavioural risk factors for malaria in the Machadinho resettlement area in the Amazonian forests of Brazil. Analysis suggests that economic status and knowledge of the importance and behaviour of the mosquito in transmitting malaria are significant factors in determining prevalence risk, irrespective of whether preventive precautions (DDT spraying of houses, and clearing vector breeding sites) are undertaken in the endemic area. However, a higher economic status combined with better knowledge of the vector and DDT spraying decreases the risks of infection considerably. The results suggest that economic status--which is not easily subject to intervention--plays a more important role in transmission than is normally suspected, although preventive actions diminish the disease burden significantly. One might conclude that the landless and impoverished migrants who seek income, and independence in the jungle are destined to have malaria as one of their many burdens. A more positive implication is that control programmes must work harder and more intensively on behalf of poorer migrants in order to diminish the disease burden for these groups.