Neonatal screening for sickle cell disease has been established in three hospitals in the Eastern Province of Saudi Arabia. In the first 17 months of this programme, 5630 cord blood samples were screened with the detection of 47 babies with an FS phenotype. The sickle cell trait occurred in 4.4% births in Al Khobar, in 6.7% in Dammam and in 17.9% in Qatif. An apparent excess of the FS phenotype over that predicted from the observed S gene frequency occurred at all three centres. The cause of this excess remains unknown although a high prevalence of sickle cell-beta o thalassaemia and the effects of non-random mating may be contributory factors.