The epidemiology of Hymenoptera venom allergy in Europe showed prevalence of systemic reactions of about 3%, but is scantly investigated in Italy. We studied two samples of the general and an at risk population, i.e. the foresters, in northern Italy. A standardized questionnaire dealing with allergic reactions to Hymenoptera stings was submitted to the subjects included in the study, who were factory workers in Milan and Verona and foresters in Lombardy. An overall number of 574 subjects participated to the study, 462 (299 males and 163 females, mean age 40.1 yrs, range 20-63 yrs) were factory workers and 112 (all males, mean age 38.8 yrs, range 24-59 yrs) were foresters. Among factory workers, 302 (65.4%) were stung by Hymenoptera, 49 (10.6%) had had large local reactions, and 13 (2.8%) systemic reactions. Among foresters, 76 (67.8%) were stung, 11 (9.8%) had had large local reactions, and 5 (4.5%) systemic reactions. The systemic reactions were life-threatening in 3 (0.6%) industrial workers and 2 (1.8%) foresters. The prevalence of systemic reaction of 2.8% in the general population agrees with the data reported from a number of countries with temperate climate. The prevalence of 4.5% in foresters attributed to this population a risk only slightly increased.