We have studied the diagnostic reliability of the specific skin tests done in 30 subjects who presented with chronic bronchitis (CB) as the only clinical manifestation related to exposure to pigeons and in 21 subjects with CB and known risk factors. Additionally, two control groups were included (24 asymptomatic subjects exposed and sensitized to pigeons and 10 subjects not exposed and not sensitized to pigeons). The skin prick tests with pigeon serum were negative in all the subjects tested. The intradermal skin tests showed an immediate positive reaction in 16 of the 30 CB-affected patients and in six of the control group of exposed asymptomatic subjects (chi square: 3.376) (P < 0.1; nearly significant); after 6 h, a positive reaction was recorded in 14 of the CB-affected patients and in three subjects of the control group (chi square: 5.187) (P < 0.005). A delayed reaction was seen in 10/30 CB patients and in only three of the 24 subjects of the control group (chi square: 2.218) (nonsignificant). In the group of the 21 CB patients with known risk factors and not sensitized to pigeons, only two patients showed immediate skin reactivity; the remaining readings were negative. Lastly, in the control group of 10 unexposed, nonsensitized subjects, the intradermal skin tests in the different readings were negative. Our results show that although the skin tests with pigeon serum have low sensitivity, they can be a useful supplement in distinguishing cases of CB attributable to chronic pigeon exposure from those cases attributable to another cause, especially in the consideration of immediate and late readings.