Personal exposure to dust and endotoxin was measured among 198 Dutch pig farmers. For each participant 8-h measurements were made on 2 days, one in summer 1991 and one in winter 1992. Mean time-weighted average (TWA) exposure to dust was 3.0 mg m-3 (arithmetic mean, range 0.3-27 mg m-3) and mean TWA exposure to endotoxin was 130 ng m-3 (arithmetic mean, range 6-1503 mg m-3). Empirical statistical modelling was applied to identify activities and farm characteristics associated with exposure. In a multiple least-squares regression analysis, aspects of hygiene and feeding were major characteristics associated with dust exposure. Flooring and feeding were predominant characteristics explaining variation in endotoxin exposure. Activities performed frequently, like feeding and controlling, cleaning activities and activities in which very active animals were involved, such as teeth cutting and ear tagging, were associated with exposure to dust and endotoxin. The models were used to set priorities for the development of control measures to eliminate the dust and endotoxin hazard of pig farmers.