A nitrocellulose-based radioallergosorbent test (RAST) was developed and used for the determination of IgE antibodies to Candida albicans mannan in patients with atopic dermatitis, asthma and allergic rhinitis. The results were expressed as mannan-RAST index values (an inter- and intra-assay coefficient for variation of 8.0-10.2%). The normal range for mannan-RAST index values was determined in 102 non-atopic adults. Fifty-three of 78 (67.9%) patients with atopic dermatitis showed elevated mannan-RAST index values with a significant correlation to the severity of the dermatitis (r = 0.33, P < 0.01). Sixteen of 30 (53.3%) patients with asthma had a positive mannan-RAST index value; however, 12 of the 16 asthmatics (75%) who were positive also suffered from atopic dermatitis. Those who had allergic rhinitis but not atopic dermatitis showed a positive mannan-RAST index value in 12 of 32 (37.5%) cases. Nitrocellulose-RAST offered a sensitive method for the determination of polysaccharide-specific IgE antibodies in atopic diseases. The results show that high values are observed mainly in atopic dermatitis and less sensitization to C. albicans occurs in respiratory allergy.