We reviewed over 220 cases of acute carbon monoxide (CO) poisoning and now report on 17 patients whose poisoning occurred from the indoor use of propane-fueled forklifts. All patients in this series presented with neurologic symptoms or persistent headache and were given hyperbaric oxygen to resolve their symptomatology. We investigated the concentration of CO in the exhaust emissions of 12 propane-fueled forklifts used in various workplaces in our location. The average CO concentration in the exhaust during engine idling was 36,000 parts per million (3.6%). This value decreased slightly to 30,000 ppm (3.0%) at working engine speed. Measurements of exhaust flow indicate CO production rates of approximately 60 liters per minute at working engine speed. These quantities of CO constitute a significant occupational exposure risk to workers using propane-fueled forklifts in unventilated indoor environments.