Relatively few studies have investigated the prevalence of insect-sting allergy and the results of diagnostic procedures in unselected populations. The prevalence of insect-sting reactions and of venom sensitization in Greece is unknown. We report the results from a stratified random sample of 480 subjects (404 men, 76 women), aged 20-60 years. They all belonged to the ground personnel of the Hellenic Air Force. A detailed history particularly focused on the reactions to Hymenoptera stings was taken in all subjects. Intradermal skin tests (concentration: 1 microgram/ml) with three venoms (honeybee, paper wasp, common wasp) were performed. The prevalence of venom sensitization (one or more positive skin tests) was 32.7%. Sensitization appears to be more common (2.69 times) in those living in rural areas than in those living in the capital (Athens). The prevalence of systemic reactions was 3.1% (86.7% of them had positive skin tests). Large local reactions were reported by 4.6% of the subjects (77.3% of them had positive skin tests). Asymptomatic sensitization (positive skin tests to venoms) was observed in 28.7% of subjects with no history of an allergic sting reaction. We concluded that the prevalence of Hymenoptera allergy and venom sensitization in Greece is rather high compared to that of other countries.