OBJECTIVE: Previous studies have reported seasonal or monthly variation in suicide. The present study was conducted in order to determine seasonality and other significant rhythms in violent and nonviolent suicide, alone and together, and homicide. METHOD: Data on suicide, violent suicide, nonviolent suicide, and homicide (categorized according to ICD-9) for all of Belgium for the period 1979-1987 were analyzed by means of spectral analyses. RESULTS: There was a significant seasonality for suicide but not homicide. Seasonality was present in violent but not in nonviolent suicide. The number of violent suicides increased with age and was more prominent in men. The violent suicide chronograms of younger and elderly persons were quite distinct in the occurrence of peaks in March-April and August, respectively, and lows in December-January. There was no significant relationship between violent suicide and homicide. CONCLUSIONS: Seasonality in suicide is determined by significant circannual rhythms in violent suicides, which differ between younger and elderly persons.