Sickle cell disease (SCD) occurs at a high prevalence in different parts of Saudi Arabia. Several reports indicate that the disease follows a mild clinical course in the Saudi population of the eastern province of Saudi Arabia, while little is known about the disease in other parts of the country. This study was conducted on 53 children from the Saudi Arabian south-western province with sickle cell disease and 53 age- and sex-matched normal controls (haemoglobin AA phenotype). A statistically significant difference was encountered in the haematological parameters investigated in the two groups. The SCD patients were divided into subgroups with high and low Hb F levels, alpha- and beta-thalassaemia and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency. The haematological parameters were then compared in the different sub-groups. No significant difference could be demonstrated in the haematological parameters in patients with a high or low Hb F level. In patients without thalassaemia, the red cell count, total haemoglobin and haematocrit were significantly lower, while MCV, MCH and MCHC were higher. G-6 PD deficiency existed in association with thalassaemias, and apart from a reduction in MCV and MCH, no other statistically significant difference could be demonstrated. Clinical examination revealed a severe disease with several cases suffering from the hand and foot syndrome.