Allergic asthma and rhinoconjunctivitis have been reported in workers who are constantly in close contact with arthropods during the course of breeding and research. We investigated a group of ten people working with beneficial arthropods in a "bio-factory." The following tests were carried out: skin prick test with allergens present in the workplace, baseline pulmonary function test, aspecific bronchial provocation test with ultrasonically nebulized distilled water, and pulmonary function test after workplace exposure in two subjects. The results demonstrated a good correlation between skin prick test, previous RAST positive reactions, clinical symptoms, and exposure. Pulmonary function test after workplace exposure proved positive in one asthmatic subject and in one subject with rhinoconjunctivitis. It is concluded that the evidence supports the occupational nature of these allergic diseases and that there is a need for careful surveillance and environmental monitoring within the workplace.