Penicillium chrysogenum crude extract was prepared in our laboratory. The protein concentration of this allergen assessed by coomassie blue G250 stain was 44-48 mg/ml. Three protein bands P1, P2a and P2b, were obtained by PAGE. Molecular weights of the bands were 94,000, 43,000 and 25,000 respectively as compared with standard molecular weight markers. Gel filtration through sephadex G200 revealed two peaks. These fractions were monitored for absorbance at 280 nm and combined into 3 pools according to the results of PAGE. Tube 1(T1), T2 and T3 were obtained. The average size of wheals developing after intradermal skin testing showed that T2 induced the strongest reaction. Since the main component of T2 was P2a, it is supposed that P2a of P. chrysogenum extract contains the protein with the highest allergenicity.