The blood serum proteins of five species of elasmobranchs were investigated using electrophoresis on cellulose acetate strips. Qualitative and quantitative comparisons of these five shark species with humans, using blood serum protein patterns, have not been reported previously and may contribute to vertebrate comparative hematology. Migration rates and protein patterns were compared with those of human blood serum. Species differences among the five shark species exist in terms of the number of protein components present, their migration rates, and relative amounts. Serum albumins in the sharks were present in very small amounts, compared to human blood serum, and all shark sera contained one protein fraction which moved toward the cathode electrode.