To examine the relationship between overwork and the occurrence of sudden death, the relation between occupation and seasonal variation in sudden death was studied. A total of 8481 cases of sudden death (among subjects aged over 24 years) were selected from all deaths between 1984 and 1986 in the Niigata Prefecture, Japan, based on a death certificate survey. Sudden death was defined as death within 24 h of the onset of the underlying disease. We divided subjects into 4 groups according to the occupation of the householder: Agricultural workers, employees, the self-employed, and other occupations. As the incidence of sudden death in the ‘other occupation’ group did not show any significant seasonal variation, this group was considered to be a control group. Among young to middle-aged men (25-65 year old), the incidence of sudden death was higher than in the control group for agricultural workers in April and September and for employees in March and September. However, in older men (over 65) the incidence for agricultural workers was higher only in April. Among women, there was no such spring rise in the incidence of sudden death in any occupational group. The months featuring a high incidence of sudden death coincided with the busiest occupational months only for people who were actually working and not for those who had already retired. © 1997, The Japanese Circulation Society. All rights reserved.