KEY WORDS Beta thalassemia; molecular Heteroge-

semia mutations in India. ABSTRACT The present study was undertaken with the objective to study molecular heterogeneity of β thalassemia, to correlate the phenotype with the geno-type in β thalassemia cases, and to know the incidence of different β thalassemia mutations in western Mahrashtra population, from the cases referred to the Genetic Clinic, B.J. Medical College, Pune. Total of 114 subjects were studied. These included 85 (74.6%) known β thalassemia carriers, 25 (21.9%) cases of β thalassemia major and 4 (3.5%) cases of sickle thalassemia. Total of 58 (50.9%) males and 56 (49%) females were studied. Amongst the total 114 cases studied 102 (89.5%) showed presence of IVS 1-5 mutation, while 12 (10.5%) cases showed presence of cd 41/42 mutation. Amongst the population studied the types of β thalassemia prevalent are β+ thalassemia, β0 thalassemia, β+β0 thalassemia, Sβ+ thalassemia Sβ0 thalassemia. Amongst these β+ thalas-semia is the most prevalent type. Frequency of blood transfusion (B.T.) was different in thalassemia patients with different beta globin genotypes. Hematological find-ings showed that presence of cd 41/42 mutation in ho-mozygous state produces more severe phenotype than that of IVS 1-5 mutation. IVS 1-5 mutation in combina-tion with sickle mutation produces less severe pheno-type than that of cd 41/42 mutation with sickle muta-tion. The comparative incidence of IVS 1-5 mutation in W.M. population is higher than that reported for Maharashtra and T.N. Incidence of cd 41/42 mutation is similar to that found in Tamil Nadu and North-West Pakistan and higher than that reported for Maharashtra. The communities, which showed higher incidence of cd 41/42 mutation, are Muslim and Navbudha. An exclu-sive occurrence of IVS 1 5 (G-C) and cd 41/42 mutations in Western Maharashtra population will help us to pre-vent beta thalassemia by prenatal diagnosis