Trichophyton mentagrophytes var. quinckeanum is a zoophilic form of T. mentagrophytes. It induces murine favus in the form of coarse yellow scutules bigger than 1 cm in diameter. In March, 2002, a 52-year-old male patient was examined at the Dermatology Clinic of the Medical Faculty in Kosice with a 1-week anamnesis of a solitary, oval, annular focus, 3 cm in diameter, on the right side of his face, located subauricularly. When providing the history, he has mentioned that his 12-year-old son has a ,,similar skin disease". Clinical examination of the son showed similar annular oval lesion, size about 2 x 3 cm, located in the right chest region. Since January 2002 the family has kept a guinea pig. They have obtained it through a mediator from the Kosice ZOO. The material for mycological examination was taken from peripheral parts of the foci or desquamating lesions from the father, son, and the guinea pig. Scales were examined microscopically in 20 % KOH solution with Parker's blue-black ink. The findings proved the presence of septal hyphae and formation of arthrospores. Thus, dermatomycosis was confirmed in the father and son, caused by T. mentagrophytes var. quinckeanum, the source of which was a pet guinea pig (Fig. 3, Ref. 17).