In a study of beta thalassaemia in the Asian Indian immigrant populations in the U.K., 23 out of 125 beta-thalassaemic chromosomes (18%) were of the Indian deletion beta type (600 bp deletion involving the 3' end). The individuals with beta thalassaemia had originated from various parts of India and Pakistan. However, all those individuals with deletion beta thalassaemia were from Sind and the adjacent area of Gujarat. Analysis of restriction fragment length polymorphisms in the beta globin gene cluster showed that all the 23 deletion beta thalassaemia chromosomes had an identical haplotype. These findings suggest a single origin for the Indian deletion beta thalassaemia.