Full text can be accessed at http://www.ajol.info/index.php/huria/article/view/86055Rufiji District is an area with endemic and perennial malaria. The aim ofthis study was to assess the factors contributing to increased malaria risk in thestudy area. The factors investigated included; mode of house construction,protection against mosquito bites and human behaviour. Parameters recorded forevaluating the mode of house construction were; type of wall, roofing materials,presence of open eaves between wall and roof and the type of window. Structuredquestionnaires were used to assess household mosquito avoidance behaviour andutilization of bed nets. Medium scale behavioural surveys were carried out todetermine time spent by individuals outdoors during the night. This was then plottedagainst mean hourly mosquito catches. Generally, house constructed using mud,grass, palm walls, and roofs made of grass/palm thatch, houses with no or openwindows and without mosquito gauze and houses with open eaves and lowutilization of bed nets (treated and untreated) were common over the entire studyarea. Of the 2,423 houses walls examined; 90% were constructed using mud, 61%were roofed using grass, 98% had eaves between wall and roof, and 49% had nowindows while 45% of windows had no mosquito gauzes. There were highlysignificant differences (p < 0.001) within all the above variables investigated. Only21% of the households used bed nets of which only 7.5% were insecticides treated.There were highly significant differences (p < 0.0001) within variables investigatedon mosquito avoidance behaviour. Most individuals, both children and adults,remained outdoors up to 22.00 hrs. Environmental factors, poorly constructedhouses, low rate of utilization of bed nets and other protective measures, andpoverty were identified as risk determinants for malaria in the study area.Intervention measures relevant to the study area are discussed.