Presuming that overtime work may associate with chronic fatigue and then decrease cardiovascular function, this report was prepared to find out the definite positive relationship between long working hours and subjective fatigue complaints. We analysed the data of a field survey of 238 men who were working at the department of research & development of three electronics manufacturing companies in S. Korea. The field survey consisted of self-report questionnaires on the working hours, health conditions, and fatigue. For data analysis, the subjects were divided into 3 groups on the criteria of 60 and 70 working hours per week: less longer (LLWH), longer (LWH), and more longer (MLWH) working hour groups. We compared the age-adjusted mean % scores of fatigue complaints among LLWH, LWH, and MLWH. The rate of complaints of subjective fatigue before going to work for LWH and MLWH tended to be significantly higher than those for LLWH. Hence, we conclude that the questionnaire on the subjective fatigue complaints is a good screening tool for early detection of cumulative fatigue due to chronic job stress such as long working hours.