It is assumed that differences in the mortality rates of occupational groups are explained by work-related factors, socioeconomic status, and health practices, etc. The present study focuses on the common factors contributing to differences in the mortality rates from all and major specific causes among Japanese male occupational groups. With respect to mortality rates, the following conditions were adopted as major specific causes of death: cerebrovascular disease (CVD), ischemic heart disease (IHD), stomach cancer (Stomach CA), lung cancer (Lung CA) and suicide. Occupations were classified into eight groups. Age-adjusted mortality rates due to each specific cause of death were calculated, using the age-specific population in 1985 as a standard, for every five years of census from 1965 until 1995. The number of significant correlation coefficients and their magnitude between mortality rates due to major specific causes, among the eight occupational groups, increased with advancing census year. Namely, the order of mortality rates for the major causes in Japanese male occupational groups became more similar over the recent 30 yr period. According to the principal component analysis of mortality rates due to major specific causes, the first main factor contributed 57.9% of the commonality in 1965, 76.5% in 1980, and 86.0% in 1995, respectively.