From 1965 to 1991 the percentage of arsons in relation to all crimes increased fivefold; and in the same time period, the amount of arson increased nearly tenfold. According to the police in Finland, there are over 700 arsons committed every year; 90 percent are committed by men. The percentage of women arsonists, however, has increased 0.2 percent annually. Women today commit approximately 10 percent of arsons, and juveniles commit 10-15 percent of all arsons. The arsonists differed from the homicide offenders regarding rural residence (P = 0.009), poor education (P = 0.004), suicidality (P = 0.001), alcohol problems (P = 0.002), and psychiatric care (P = 0.00002). Arsonists were also more often found not to be legally responsible for the crime committed due to mental illness (P = 0.01). The author concludes that because of the increasing arson trend, various branches of science should pay more attention to acts of arson. Psychiatric examination and mental treatment of arsonists are especially challenging, because the firesetters generally have more mental disorders than other offenders. 1 table, 3 figures, and 22 references