Acrolein is an aquatic herbicide used in the western United States to prevent impaired water flow in irrigation canals. Despite its toxicity, few cases of acrolein-related illness have been reported in the literature. On August 15, 2012, an irrigation district notified the Washington State Department of Labor & Industries (L&I) of acrolein-related illness in one of its pesticide applicators. L&I inspected the site and interviewed the exposed worker, coworkers, and employer. The Washington State Department of Health assisted by obtaining medical records, interviewing the patient and hospital staff, and reviewing information obtained from L&I. To look for additional cases, CDC reviewed data from the SENSOR-Pesticides program* and the California Department of Pesticide Regulation for 1993-2009, the most recent years of data availability, and identified seven additional cases of acute acrolein-related illness.