An indoor shiitake-mushroom (Lentinus-edodes) farm was evaluated after respiratory illness was reported by workers at the facility. The study was conducted in 1989 and involved two site visits. During the first visit, a questionnaire was administered privately to each of 14 hourly employees involved in cultivation of mushrooms on oak logs. Bioaerosol sampling was conducted at various locations in the facility during the second visit. A short term air sample for airborne spores using a filter cassette, and bioaerosol sampling was accomplished with Andersen two stage microbial impactors/impingers (AGI-30). Results showed that nine women and five men had worked at the farm for periods ranging from 1 to 32 weeks (wk). Seven were current smokers. Seven workers reported being treated for respiratory illness without improvement of symptoms. Of the 14 workers, 11 reported 15 or more symptoms (dry cough, nasal discharge, dyspnea, and sneezing followed by chest tightness). Filter cassette sampling revealed a concentration of 3.3 x 10(6) spores/cubic meter at the center of the room. About 5 x 10(7) spores/square centimeter were counted on a section of filter from one of the air conditioning units in the mushroom growth room. The morphology was consistent with those of shiitake spores. Aerosol samplings yielded various mesophilic and thermophilic bacteria as well as other mold spores including Penicillium from several regions of the facility. The authors conclude that exposure to oak dust alone seems to be an unlikely cause of the respiratory illness reported, and that exposure to allergenic mold and mushroom spores was the likely cause. The authors recommend the use of respiratory protection, disposable uniforms and garments, and a medical surveillance program to review and evaluate the situations every 6 months.