Taxonomic revision of the genus Striga in Africa revealed 34 taxa of which 79% are endemic. Higher species diversity is shown for the tropical grassland north of the equator. The number of species found in the region from Senegal to eastern Nigeria is equivalent to that of the entire region south of the equator, 58% of taxa. It appears that the number of taxa and the rate of endemism in Africa decreases from west to east and also from north to south. The trend of decreasing species diversity extends to the Arabian Peninsula and southeast Asia. Special attention has been given to the problem of the development of host-specific strains in S. gesnerioides (Willd.) Vatke and S. hermonthica (Del.) Benth., wide ranging and serious pathogens of numerous crops in the Sahel of Africa. While these strains may have distinct morphotypes, we accord them no taxonomic status. Striga asiatica (L.) Kuntze, S. hirsuta Benth., and S. lutea Lour. are conserved as distinct species while S. baumanii Engl. is excluded from the genus. Striga linearifolia Hepper is proposed as a subspecies of S. bilabiata (Thunb.) Kuntze.

Key words: Africa, Scrophulariaceae, Striga, Tropical Grassland