Cytogenetic studies were carried out on the blood/bone marrow samples of three patients with chronic granulocytic leukaemia (CGL) and one patient with Burkitt's lymphoma. The karyotypes determined were 46, XY, Ph+ for patient O. A; 46, XY, t(9q+, 22q) for T. A. and 46, XX, t(9q+, 22q) for patient E. O. Patient O. L. with Burkitt's lymphoma presented two karyotypes: 46, XY and 46, XY, +18. The results showed that Philadelphia (Ph1) chromosome was detected in all the patients with CGL and a chromosome marker for African Burkitt's lymphoma in the boy with the disease.