The mild course of the diseased state of haemoglobinopathies and the thalassaemias in Arabia and the interaction of the genetic abnormality and environmental factors are particularly interesting as the Peninsula exhibits a diverse climate and topography that encourages study of thei interactions between various genetic and environmental factors.The present study is aimed at elucidating the incidence and frequency of these genetic abnormalities in various regions of Saudi Arabia. The relationship between haemoglobinopathies, thalassaemia and glucose-6-phosphate dehydrogenase deficiency on the one hand and malaria parasites on the other are elucidated. The results are presented in the light of the environmental factors prevailing in the area.