RESUMEN
Cytological and cytogenetic observations are recorded on Jamaican dogs with spontaneous transmissible venereal tumour. Fixed tissue from 22 dogs was examined for pathological study and sex chromatin, and fresh tissue and exudate from the tumour from 9 dogs were examined for cytological features, and chromosome studies. The pathological appearances exclude this tumour from the lymphoma group and show 2 distinct cells, the tumour cell and a lymphoid element. These 2 cell types are seen in the exudate and fresh tissue. The lymphoid cells show no sex chromatin body. The tumour cells show a body which occurs independently of the sex of the animal in 10-30 percent of cells and is thought to be a nucleolus. The chromosome number and karyotype is 58 or 59 with a similar pattern to that seen in the United States and Japan. The aetiology is discussed in the light of these findings and the relative isolation of Jamaica in the canine world.(AU)