Intracutaneous, nasal provocation (NPT) and radioallergosorbens (Phadebas RAST) tests were performed on 49 subjects hypersensitive to cats and (or)dogs using serum albumin and epithelium extracts from cats and dogs. Serum albumin elicited intracutaneous reactions in most of the subjects, but gave positive NPT und RAST results in only a few and was, therfore, of limited clinical importance. The intracutaneous tests with epithelium extracts were positive in some subjects in whom other tests had been negative. It is possible that these false-positive skin tests were caused by serum albumin present in the extracts, while in others non-specific skin reactions were apparently caused by epithelial components. On the other hand, the results suggest that the few patients allergic to dogs were incorrectly diagnosed with the RAST. But the described in-vitro method increases the chances of diagnosing allergies against animal epithelia. It is furthermore useful in the interpretation of equivocal skin tests.