Seventy-one Saudi and Yemeni Arabs with sickle cell anaemia from western Saudi Arabia aged between 1 1/2 and 42 years were studied. The mean steady state haemoglobin concentration of 8.1 g/dl was lower than that of 10.7 g/dl reported previously for sickle cell anaemia in eastern Saudi Arabia. The patients were divided into an SSLF group with fetal haemoglobin (HbF) of 10.0% or below (44 patients) and an SSHF group having HbF above 10.0% (27 patients). No significant differences were found in the haemoglobin concentrations, haematological indices and incidences of bone changes of the two groups. SSLF patients were significantly more prone to infections (P less than 0.01), however. Also, there was an overall high incidence of hepatomegaly (69.0%) and splenomegaly (54.9%) and hepatomegaly was significantly more common in the SSLF group (P less than 0.02). Many of the patients, even with HbF levels over 10.0%, did not follow a benign course and suffered from severe anaemia, infections of the respiratory and urinary tracts, bone pains and infarcts, or bossing of the skull. Rarer complications included hepatic crisis, chest syndrome, retinal haemorrhage, epistaxis and hemiplegia. It is therefore apparent that Saudi Arabian sickle cell anaemia, even in patients with raised haemoglobin F levels, may be as clinically severe as in African patients.