Electrophoretic study of two species of Moniezia cestodes, M. expansa and M. benedeni, sampled in African (Senegal) domesticated ruminants, revealed a complex of species and a degree of specificity more pronounced than that previously described. The status of the different species is validated by the probable occurrence of within species cross-mating. A European origin is suggested for M. expansa due to identical isoenzyme patterns in cestodes from France, whereas some atypical individuals may be derived from wild African ruminants.