Regions of the promoter and exons 5-8 of the tumour suppressor gene p53 were analysed in 25 cases of sporadic bovine leucosis. The study included 17 cases of juvenile leucosis, five cases of adult leucosis and three cases of skin leucosis. Exon 2 of tumour suppressor gene p16 was also investigated in the same samples. No sequence variations were present in the analysed areas of the genes. In p53, this fact represents a clear difference in comparison with enzootic bovine leucosis. In p16, no comparative data are available.