Incidental catches of harbour porpoise by commercial fisheries in the Estuary and Gulf of St. Lawrence, Canada were examined. Two questionnaires, one in 1989 and one in 1990, were sent to all active fishermen, asking for information on the number of porpoises caught during the previous season, gear type and mesh size, location and time of catch. Out of 968 questionnaires sent in 1989 and 731 in 1990, 33% and 18% respectively were returned completed. In both years, 29% of the fishermen said they had caught one or more porpoises during the previous year. The 316 responses to the first questionnaire indicated that 623 porpoises were caught during the 1988 fishing season for a mean of 1.97 (SD=6.3) porpoises per fisherman; the 135 responses to the second indicated that 326 animals were caught (mean 2.41; SD=10.9). Catches were mainly in gillnets set for cod (Gadus morhua), in July, near shore, but some porpoises were caught in all months from April through November. On average, for both surveys combined, 7% of fishermen said they had caught other cetaceans and 49% said they had caught seals. A total of 148 porpoise carcasses were retrieved from fishermen in 1989. The mean length of males was 135cm (SD=14.8) (n=64) including some large specimens (9>160cm).