The frequency of the mutant gene for sickle cell is widely distributed in the sub-Saharan Africa, the Middle East and the Indian subcontinent. There is epidemiologic evidence that sickle cell trait confers a survival advantage against malaria and that the selection pressure due to malaria has resulted in high frequencies of the mutant gene in areas of high malaria transmission. Kisumu West District has been used for a number of vaccine trials and other epidemiological studies. We carried out a study to look at the relationship between sickle cell trait, age, haemoglobin level and malaria parasite density.