Harbor porpoises (Phocoena phocoena) have been killed in gillnets set for halibut in central California since at least 1969. In the Monterey Bay area (Pigeon Pt. to Pt. Sur), past estimates of mortality have ranged from 25-55/yr. In the spring of 1989, many dead harbor porpoises began washing ashore with evidence of gillnet entanglement. Observer records from the California Department of Fish and Game and stranding data indicated that a minimum of 53 harbor porpoises were killed in Monterey Bay gillnets in 1989, and it is likely that the total number killed in this area was several hundred. Two-thirds of the specimens were immature. If Monterey Bay harbor porpoises form a resident population, such high takes in the future threaten to decimate the population. We recommend closing the fishery or setting quotas and monitoring the kill with approximation of 100% observer coverage.