Chief operators at the Chernobyl power plant were assessed at four time points after the nuclear disaster and compared to a comparable group of chief operators at another nuclear power station. MMPI findings demonstrated a significant increase over time in health concerns, depression, and other indicators of stress in those operators working at the station at the time of the assessment. There was also an increase in the proportion with at least one MMPI clinical scale in the abnormal range. The authors hypothesize that the continuing uncertainty of the safety of working at Chernobyl may have contributed to these findings by either increasing the stress levels of those who remained at this power station, or through attracting workers who were less well adjusted before volunteering to work there