In this study the prevalence of the different beta-thalassaemia types in southern Sardinia was investigated by cellulose acetate and agar gel electrophoresis or globin chain synthesis analysis on column chromatography or both in (1) all the patients (347) presenting with thalassaemia major or intermedia at our haematology service from 1976 to 1979, and (2) a group of 82 patients with transfusion-dependent thalassaemia major randomly chosen from 236 under our care. Apart from six subjects with delta(beta)0/beta+-thalassaemia genotype and eight with beta0/beta+ or less probably beta+/beta/-thalassaemia, all thalassaemia major and intermedia patients studied were beta0-thalassaemia homozygotes. Globin chain synthesis on peripheral blood cells from these patients, performed at different intervals from blood transfusion, showed no incorporation of radioactive leucine into beta-globin peak, the same as before the transfusion. No correlation between kappa/gamma ratios and clinical severity or hypersplenism was found. Globin chain synthesis analysis carried out at birth in three infants later found to have homozygous beta0-thalassaemia demonstrated imbalanced or borderline kappa/gamma ratios.