BACKGROUND ABO blood group iso-antibodies are naturally occurring antibodies found in serum and other body fluids. METHODS Serum, saliva and milk samples from 5 mothers identified as "Bombay" phenotype were tested for ABH-iso-antibodies by routine serological techniques. RESULTS All the five mothers showed presence of iso-antibodies in the samples tested. Higher titer values in milk than their serum were observed on subjects whose samples were collected in immediate post-partum phase as compared to those whose samples were collected after a lapse of a few months. CONCLUSIONS High titer iso-agglutinins against ABH antigens were detected in milk samples besides their presence in saliva as well as serum.