100 diabetic and 100 diabetes-free patients were mycologically examined for the presence of pathogenic fungi in their toe-webs and toe-nails. While there were clinical signs of presumed mycotic infection in 73 of the diabetic and in 66 of the non-diabetic subjects, the examination of the KOH-treated specimens revealed fungal elements in only 70 of the former and in 53 of the latter group. Isolation of the causative agent was possible in 57 of the diabetic patients (T. rubrum in 46%, C. albicans in 31%, T. mentagrophytes in 21% and E. floccosum in 3%) and in 40 of the control group (T. rubrum 57,5%, T. mentagrophytes 35%, C. albicans 5%, E. floccosum 2,5%). An interesting correlation was observed between the level of blood sugar and the percentage of positive fungal findings, the patients with more than 3000 mg/ml being 100% afected. C. albicans was found in a lower percentage in non-diabetic patients. The in vitro test of the sensitivity of the isolated organisms to the antidiabetic drugs, received by the patients, showed no significant anti-fungal activity.