A group of Yemeni patients with sickle-cell disease (SCD) and normal Hb AA individuals living in Riyadh were studied to determine the incidence of the alpha-gene molecular defect. Blood samples were obtained from 26 SCD patients and 19 controls (the Hb AA group). In the SCD patients the frequency of single alpha-gene deletion (-alpha/alpha alpha) was 0.346, compared to 0.263 in the Hb AA group. The frequency of two gene deletion (-alpha/-alpha) was 0.231 (0.0 for the Hb AA group). In one Hb AA case, a triple alpha-gene arrangement (alpha alpha alpha/alpha alpha) was found (frequency 0.053). The results suggest that alpha-thalassaemia occurs frequently in Yemeni SCD patients. Further studies to determine the overall frequency of alpha-thalassaemia in the Republic of Yemen would be of value for patient management.