Seed proteins of individual plants from 14 populations of Striga hermonrhica growing on sorghum, millet, maize and wild grasses in Burkina Faso, Mali and Niger were studied using gel electrophoresis in order to assess the population structure and genetic diversity of the parasitic weed. The relative intensity of the different bands within a pattern was used to depict the genotypic constitution of each sample. Genotypic frequencies conformed to Hardy-Weinberg expectations in 13 populations out of 14 for the two loci that were interpreted. Heterozygote deficiencies could be the result of the Wahlund effect. The genetic divergence between populations appears to be low for both Adh and Got loci. Thus, the physiological specialization for a particular host could be a recent phenomenon. A low host specificity of S. hermonthica populations could affect the efficiency of introducing new resistant cultivars as a control measure against the parasitic weed.