In Switzerland, the number of completed homicides has varied in the last 30 years between 46 and 110 cases per year. On average, 13 percent of the homicides have been unsolved. The Swiss Homicide Database, which covers more than 1300 completed homicide cases committed between 1980 and 2004, has been used to study their characteristics. The data show that unsolved murder cases occur more often in public than in private places and involve predominantly unmarried men under 40, of foreign nationality or of homosexual orientation. A logistic regression showed that the strongest predictors are the sexual tendency of the victim and the location of the event.