In August 1992, four farm workers in Minnesota died in two separate incidents after entering manure waste pits: two were poisoned by hydrogen sulfide gas, and two were asphyxiated. The Minnesota Fatality Assessment and Control Evaluation (FACE) program was notified of the incidents by the state Occupational Safety and Health Administration and the Minnesota Farming Health Project, respectively. This report summarizes the investigations of these two incidents by the Minnesota FACE program and CDC's National Institute for Occupational Safety and Health (NIOSH) FACE personnel.