In order to determine the main aetiologies associated with thrombocytopenia in a hospital setting of Cameroon, 180 adults with platelet counts <100x10(9)/L were examined and screened for a full blood count, thick and thin blood films, basic coagulation tests (activated partial thromboplastine time, a one-stage Quick's prothrombin time and a bleeding time), an HIV screening test as well as a bone marrow aspirate using standard methods. Other tests were selectively done as dictated by the suspected diagnosis. The major clinical findings among 180 cases included fever >37.5 C (53.9%), splenomegaly (45.6%) and haemorrhage (30.6%). The main laboratory findings were anaemia (defined as haemoglobin (Hb) <11g/dL) in 80.6% of cases and a positive thick blood film (all confirmed to be P. falciparum) in 30.6% of cases. Out of the 18 different aetiologies associated with a low platelet count in the group studied, malaria appears as the unique cause in 22.2% of cases. Petechial bleeding, bruising and epistaxis were the major forms of bleeding involved (69.1%, 27.3%, and 23.6% respectively). However, only 3 cases diagnosed with malaria showed any form of bleeding (mean malaria parasite densities >15,000/muL of blood in each case). No other haemostatic abnormalities were observed. It may be cost-effective for patients with low platelet counts in malarial regions to be systematically screened for malaria parasites.