The cardiotoxic potential of 1,1,2-trichloro-1,2,2-trifluoroethane (76131) (FC113) in producing cardiac dysrhythmias among workers in the aerospace industry was investigated. Simultaneous exposure and ambulatory electrocardiograph (ECG) studies were conducted on 31 workers involved with the cleaning of rocket and ground support equipment for the National Aeronautic and Space Administration. Control data were obtained from 16 workers on nonexposed days. A variety of ECG data including ventricular premature beats, supraventricular premature beats, atrioventricular block, t-wave inversions, ST segment depression, length of P-R interval, and fluctuations in heart rate were monitored. Results showed that exposures below the OSHA 8 hour time weighted average of 1000 parts per million did not generate any cardiac dysrhythmias or even subtle changes in heart activity in these workers. The authors caution that the extension of these results to other populations of workers, in particular, to those involved in stressful or highly physically demanding jobs, may be limited.