A brief survey of alluvial pools and irrigated ricefields in The Gambia shows that the distribution of Bulinus senegalensis is not confined to laterite pools and is similar to that in neighbouring Senegal. B. senegalensis was found in every site at least once, alone or with B. forskali. The proportion of the two species varies during the season and from year to year. It is no longer necessary to consider B. forskali as a natural host of S. haematobium.