The role of Basidiospores in the allergic diathesis is poorly understood. Dialyzed extracts of Agaricus campestris, Coprinus micaceus, Fuligo septica, Lycoperdon perlatum, Scleroderma lycoperdoides, Ustilago maydis, and sooty mold were prepared from fresh spores. The study group consisted of 100 patients with asthma and 100 patients with allergic rhinitis. These 200 patients had symptoms occurring during October and November. All were intradermally skin tested with the seven extracts at concentrations of 1 microgram/mL or 10 micrograms/mL. No scratch or pressure puncture tests were performed. Skin tests were recorded at 15 minutes (pos = 5-mm wheal with 10-mm erythema or greater) and at six or 24 hours (pos = 6 mm or greater of induration and erythema). A total of 436 immediate reactions were observed in the asthmatic group (4.4/patient) compared with 129 in the rhinitic group (1.3/patient). The late phase reactions were just the opposite. The asthmatic group had 66 late phase reactions or 0.7/patient compared with 382 or 3.8/patient in the rhinitic group. This study demonstrates that patients with bronchial asthma have a higher incidence of immediate skin sensitivity by intradermal testing, whereas patients with allergic rhinitis have late phase sensitivity to these fungal spores. This study was performed in the eastern United States only; therefore, the clinical significance of the results will become more apparent once this study is repeated in other parts of the country by other investigators.