To determine the association between haematological malignancies and the HIV-1 in Yaoundé, Cameroon, adult patients (> 16 years) followed up in the Haematology Clinics of two major hospitals were screened for the HIV between 1994 and 1999. There were nine haematological malignancies diagnosed among the 172 patients including Non Hodgkin's lymphomas (31.9%); chronic lymhocytic leukaemia (21.5%); chronic myelogeneous leukaemia (18.0%); acute myelogeneous leukaemia (9.9%); acute lymphoblastic leukaemia (7.6%) and multiple myeloma (7.0%). Burkitt's lymphoma, Hodgkin's disease and myelodysplastic syndrome were less frequently diagnosed. Forty-five of all cases (26.2%) had antibodies to the HIV-1 virus, predominantly in patients with Non-Hodgkin's lymphomas (p < 0,001, OR = 5.8, adjusted for age; CI = 2.7 - 12.4). About 19.4% and 11.8% of cases with chronic and acute myelogenous leukaemia respectively were HIV-1 positive. Although B-lineage-derived malignancies are more often associated with the HIV infection, other malignant proliferations of the haematopoietic system may not be coincidental.