Statewide surveillance in California determined that the highest drowning rate from 1980 through 1989 was for the rural, desert county of Imperial (21.9 drownings per 100,000 population). To identify activities associated with drowning in this county, the authors abstracted data from the county sheriff-coroner's reports. From 1980 through 1990, there were 317 unintentional drownings; 85 percent occurred in irrigation canals. The activity prior to drowning was known for 262 persons (83 percent), and the most common activity was illegal entry into the United States. Overall, 140 persons (53 percent) were illegal entrants. Ninety-three percent of illegal entrants drowned in the All American Canal; the monthly drowning rate increased as the monthly average water velocity in the canal increased (r = 0.36; P < 0.001). Forty-eight persons (18 percent) drowned while riding in or on a land vehicle (automobile, pick-up truck, motorcycle, dune buggy, or tractor), the second most common activity associated with drowning. Seventy percent of the 23 drivers had an alcohol concentration of 100 milligrams per deciliter or more, California's limit for intoxication. To reduce drownings in Imperial County, prevention strategies should target persons engaged in at-risk activities near bodies of water. These strategies should include the identification and use of effective canal safety devices.