25 skin basaliomas were studied immunohisto-chemically using 6 different monoclonal antibodies (MAB) to the low-molecular cytokeratins N 8, 18 (according to Moll's catalog) as well as to the cytokeratins N 1, 2, 9, 10, 11 and N 17. Prekeratin N 17 was found in all tumours while cytokeratin N 18 was found in no tumour. Prekeratin N 8 was expressed in 24 % of tumours. MAB EE 21-06 to the cytokeratin N 1, 2, 9, 10, 11 are reactive with tumour cells in 20% of cases. Basalioma cells (apart from trichobasalioma) did not react with MAB G 36-19. These results suggest a dissimilar origin of basaliomas and may help in the differential diagnosis of the skin malignant tumours.