BACKGROUND: The seasonality of suicide rates and methods of suicide may be related to changes in weather and conditions of employment. Particularly the amount of occupational outdoor exposure could show differences in the distribution of suicides by season and the selection of suicide method, in addition to age at the time of death. METHODS: The data consisted of all death certificates (n=1359) of completed suicides in the province of Oulu, Finland, during the years 1988-1999. For male subjects included in this study, four occupational groups were identified according to decreasing occupational outdoor exposure. The mean ages, the distribution of suicide methods and the seasonal variation in suicides for each occupational group were analyzed. RESULTS: Farmers were significantly older at the time of suicide than construction or indoor workers, and farmers employed significantly more violent methods than the other occupational groups. In the spring, farmers had a significant peak in the rate of suicides. In the winter, forest workers had a significant trough in the rate of suicides. In the summer, indoor workers had a significant peak in the rate of suicides. LIMITATIONS: The analyses were restricted to males due to the low number of females in the study population. CONCLUSIONS: The novel finding in this study was that the seasonality of violent suicides was most strongly seen as a spring peak and a winter trough among outdoor workers. The recognition of typical risk factors of different occupations, such as outdoor exposure, and occupational-related susceptibility towards certain suicide methods could benefit in the prevention of suicides.