Malaria is still a problem in the Kalibawang subdistrict. An outbreak occured in 1998. An investigation was conducted to determine the case distribution occording to man, place, and time. Other factors supporting the outbreak were also investigated. The investigation was conducted through Mass Fever Surveys (MFS), interviews to cases and puskesmas staff, field observations in 4 villages in October. Results revealed that during this outbreak two peaks occurred namely in June and October. The attack rate (AR) was 1,2%. No fatal cases were recorded. The main vectors were Anopheles aconitus and An.maculatus. Factors recorded causing the outbreak were late case finding and no vector control. Risk factors suporting malaria transmission were no mosquito proof houses, the existence of cattle in the houses, vector breeding sites surrounding human habitation, no reguler use of bednets, the behavior of being outdoors during the night and no use of any repellents.