The population of India is extremely diverse comprising of more than 3,000 ethnic groups who still follow endogamy. Haemoglobinopathies are the commonest hereditary disorders in India and pose a major health problem. The data on the prevalence of β-thalassemias and other haemoglobinopathies in different caste/ethnic groups of India is scarce. Therefore the present multicentre study was undertaken in six cities of six states of India (Maharashtra, Gujarat, West Bengal, Assam, Karnataka and Punjab) to determine the prevalence of haemoglobinopathies in different caste/ethnic groups using uniform methodology. Fifty-six thousand seven hundred eighty individuals (college students and pregnant women) from different caste/ethnic groups were screened. RBC indices were measured on an automated haematology counter while the percentage of HbA(2), HbF and other abnormal Hb variants were estimated by HPLC on the Variant Hemoglobin Testing System. The overall prevalence of β-thalassemia trait was 2.78 % and varied from 1.48 to 3.64 % in different states, while the prevalence of β-thalassemia trait in 59 ethnic groups varied from 0 to 9.3 %. HbE trait was mainly seen in Dibrugarh in Assam (23.9 %) and Kolkata in West Bengal (3.92 %). In six ethnic groups from Assam, the prevalence of HbE trait varied from 41.1 to 66.7 %. Few subjects with δβ-thalassemia, HPFH, HbS trait, HbD trait, HbE homozygous and HbE β-thalassemia as well as HbS homozygous and HbS-β-thalassemia (<1 %) were also identified. This is the first large multicentre study covering cities from different regions of the country for screening for β-thalassemia carriers and other haemoglobinopathies where uniform protocols and methodology was followed and quality control ensured by the co-ordinating centre. This study also shows that establishment of centres for screening for β-thalassemia and other haemoglobinopathies is possible in medical colleges. Creating awareness, screening and counselling can be done at these centres. This experience will help to formulate a national thalassemia control programme in India.