Fucolipids with human blood group H activity were isolated from several dog small intestines. On the basis of mass spectrometry, periodate oxidation, enzyme degradation, methylation, and immunologic studies the following structure is proposed: Fucα(1→2)Galβ(1→4)Glc- NAcβ(1→3)Galβ(1→4)Glc-ceramide. The ceramide was shown by mass spectrometry to contain hydroxyhexadecanoic acid and phytosphingosine as major constituents. © 1975, American Chemical Society. All rights reserved.