The influence of the heterologous acid secretory Candida proteinases on the adherence of the non-proteinase secreting strain of C. tropicalis DSM 4959 to epitheloid cells (vero line) was examined. The proteinases of the following Candida strains were used: C. albicans ATCC 10261 (serotype A), C. albicans ATCC 48867 (serotype B), C. tropicalis DSM 4238. The assays were performed with the previously described in-vitro-adherence test [1] using the following principle steps: Candida proteinases and C. tropicalis blastoconidia were incubated with verocells in microtest plates in phosphate-buffer in the range of pH 4.0 to pH 7.0. Adherent Candida cells were detected according to Filler et al. [2] with anti-Candida-mannoprotein antibodies and a secondary anti-rabbit-peroxidase conjugate. Compared to controls with denaturated proteinases, the photometric evaluation of adherent C. tropicalis cells showed, under optimal conditions, an augmentation of the adherence due to the Candida proteinases of about 50%. The optimum of this adherence augmentation was in the range of pH 5.5 which is outside the general activity optimum of Candida proteinases (pH 3). The degree of purity of these proteinases had no marked influence on the adherence. The specificity of the proteinase dependent adherence augmentation could be demonstrated with the enzyme inhibitor Pepstatin A. C. tropicalis blastoconidia supplemented by pepstatin A and active Candida proteinase adhered in the same range as with denaturated proteinases in control tests. Our results suggest a function of Candida proteinases in the adherence process of blastoconidia to epithelia.