In 47 allergic rhinitis patients regularly exposed to pigeons, nasal provocation tests with pigeon dropping extracts, in combination with other parameters, were performed. Twenty-five of the 47 patients developed a late nasal response (LNR) to pigeon droppings (53%), six of them an isolated response and 19 a dual response (immediate + late). The precipitating antibodies to pigeon droppings were positive in 20 (80%) and to pigeon serum in nine LNR patients (36%). Late skin responses to pigeon droppings occurred in 15 (60%) and to pigeon serum in seven LNR patients (28%). In 13 patients (52%) general malaise, in seven (28%) increased blood eosinophilia, in nine (36%) increased body temperature and in 11 (44%) haemorrhages in the nasal mucosa were observed during the LNR. The results of this study provide evidence for the existence of a new disease, a nasal form of pigeon breeder's disease.