Fungi are elements of the ontocenosis of the oral cavity and causal factors of inflammatory lesions in its mucous membrane. The objective of the study was to find differences in the activity of hydrolytic enzymes of Candida albicans isolated from patients with diseases of the periodontium and mucous membrane of the oral cavity. Of 235 patients examined, 31 were diagnosed with gingivitis, 38 with glossitis, 28 with leucoplakia, 37 with adult periodontitis, 25 with juvenile periodontitis, 36 stomatitis prothetica and 40 with stomatitis atrophica. In 196 patients (83.4 +/- 2.4%), fungi belonging to Candida species were detected. In the evaluation of Candida albicans strains (146) properties, bioMerieux API ZYM tests containing substrates for the detection of 19 hydrolases were used. All the investigated strains were characterized by the activity of 14 enzymes, i.e. phosphatase alcaline, esterase (C4), esterase lipase (C8), leucine and valine arylamidase, phosphatase acid, naphthol-AS-BI-phosphohydrolase, alpha galactosidase, beta galactosidase, alpha glucosidase, beta glucosidase, N-acetyl-beta-glucosaminidase, alpha mannosidase and alpha fucosidase. Strains isolated from the oral cavity of patients with disease of periodontium and mucous membrane are characterised by the highest phosphatase acid activity. The greatest enzymatic activity is characteristic of Candida albicans isolated from patients with stomatitis atrophica or stomatitis prothetica, and the lowest in strains from gingivitis or juvenile periodontitis cases. Differences in the activity of hydrolases are statistically significant (p < 0.01) for: esterase (C4), leucine and valine arylamidase, phosphatase acid, naphthol-AS-BI-phosphohydrolase, beta glucosidase, N-acetyl-beta-glucosaminidase, of fungi isolated from patients with particular clinical diagnoses.