Incidence of Oh and weaker A and B variants was studied in 167,404 Indians in Bombay. Eight out of 17 cases of A variants were due to weak A(2), the majority being among AB individuals. Incidence of all weak A is 1:3,300 among persons possessing the A antigen. The actual incidence of A variants deducting weak A(2) is approximately 1:6,000 persons having the A antigen. Weak B is observed in 1:9,300 persons possessing the B antigen. A(x)-B(x) variants were twice as common as A(m)B(m) types. The O(h) phenotype is observed in 1:7,600 random persons. The regional and caste distribution of O(h) individuals showed that 14 out of 22 of the Oh individuals in the present survey and 33 out of 58 among all Oh cases investigated belonged to south-west districts of Maharashtra.

Abstract. Incidence of Oh and weaker A and B variants was studied in 167,404 Indians in Bombay. Eight out of 17 cases of A variants were due to weak A2, the majority being among AB individuals. Incidence of all weak A is 1:3,300 among persons possessing the A antigen. The actual incidence of A variants deducting weak A2 is approximately 1:6,000 persons having the A antigen. Weak B is observed in 1:9,300 persons possessing the B antigen. Ax‐Bx variants were twice as common as AmBm types. The Oh phenotype is observed in 1:7,600 random persons. The regional and caste distribution of Oh individuals showed that 14 out of 22 of the Oh individuals in the present survey and 33 out of 58 among all Oh cases investigated belonged to south‐west districts of Maharashtra.

Tests on 1,000 A group Indians in Bombay showed high H content in 5%. This incidence was the same in Maharashtrians and Gujarathis. A(1) subjects with high H had a mean score for A(1) antigen of 22.54 (Dolichos) which was slightly more than or equivalent to A(1) individuals (19.66). Ulex gave a score of 9.7 in comparison to 0.55 for A(1) and 16.5 for A(2). Absorption studies confirmed higher A and H antigen expression than in A(2) and A(1) individuals, respectively. Family studies of eight A(1)/high H individuals showed no specific inheritance pattern. Various hypotheses to explain the irregular inheritance pattern have been discussed.

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Abstract. Tests on 1,000 A group Indians in Bombay showed high H content in 5%. This incidence was the same in Maharashtrians and Gujarathis. A1 subjects with high H had a mean score for A1 antigen of 22.54 (Dolichos) which was slightly more than or equivalent to A1 individuals (19.66). Ulex gave a score of 9.7 in comparison to 0.55 for A1 and 16.5 for A2. Absorption studies confirmed higher A and H antigen expression than in A2 and A1 individuals, respectively. Family studies of eight A1/high H individuals showed no specific inheritance pattern. Various hypotheses to explain the irregular inheritance pattern have been discussed.