Serial skin testing has been carried out with a mixture of bee, wasp, and yellow-jacket whole-body extracts in three groups of patients: insect hypersensitive, atopic noninsect sensitive, and nonatopic subjects. No significant differences in reactivity have been demonstrated between these three groups. Some qualitative differences may exist but the data are at best suggestive on this point. It would appear that the diagnosis of hypersensitivity to stinging insects must be based on historical considerations alone. Skin testing remains of value, however, because it is important as a guide to appropriate dosage in hyposensitization therapy.