High-yielding cowpea (Vigna unguiculata) cultivars were analysed for major changes in seed protein types, amino acid profiles and antinutritional factors content. As usual, the globulins constitute the major seed proteins (493.2–573.3gkg−1 total seed protein), followed by albumins (201.0–248.0gkg−1), basic glutelins (119.1–154.3gkg−1), acid glutelins (82.4–92.3gkg−1) and prolamins (13.2–20.2gkg−1). The electrophoretic patterns of seeds and protein fractions for all cowpea cultivars resembled to each other both qualitatively and quantitatively. However, they showed slight differences in the amino acid composition with common prevalence of glutamine/glutamic acid, asparagine/aspartic acid and phenylalanine+tyrosine. The methionine+cysteine contents were low for all cultivars and their protein fractions. Trypsin inhibitory activity varied among the cultivars and was much higher in the albumins (198.67–393.43gkg−1protein). Haemagglutinating activity was also higher in the albumin fraction and varied from 30,900 to 444,400HUkg−1 flour. In conclusion, all cultivars showed the usual compositional characteristics of V. unguiculata, but the content of antinutritional factors differed among the cultivars although they remained concentrated in albumin and globulin fractions.