Because of the variability of human milk carbohydrate composition, we determined the discriminant carbohydrate components of the milk of 18 mothers according to their ABH and Lewis secretor types during the first week of lactation. Comparative chromatograms revealed that the presence of neuraminyloligosaccharides is linked to the ABH secretor groups, and that the absence of oligosaccharides with Lea or Leb specificity is linked to the Lewis nonsecretor types. The study of carbohydrate composition according to donor secretor types consisted of measuring 16 variables from 69 samples. Analysis of variance showed significant differences between groups: high levels of N-acetylneuraminic acid and low levels of galactose distinguished ABH secretors from nonsecretors (p less than 0.001). In the ABH secretor groups, A and H secretors had higher N-acetylglucosamine contents than B and AB secretors (p less than 0.001) and lower galactose levels (p less than 0.001). The Lewis secretor groups were distinguished by significantly higher fucose levels (p less than 0.001). The ABH(+)Le(a-b-) group had higher lactose contents than the other groups (p less than 0.01).