Six species of Ulva, U. atroviridis Levring, U. capensis Areschoug, U. fasciata Delile, U. lactuca L., U. rigida C.Agardh and U. uncialis Kutzing, have been reported to occur in the south western Cape Province. As a result of herbarium, field and culture studies it was found that five of these species do occur, but U. uncialis is a synonym of U. riqida (Agardh, 1883). Furthermore, U. atroviridis has correctly been reassigned to the genus Enteromorpha (Wynne, 1986). U. rhacodes (Holmes) Papenfuss, which has hitherto only been reported from the eastern Cape Province, was also found, giving a total of five species of Ulva in the region, which are described in detail. Chloropelta caespitosa Tanner, a new genus and species, previously only recorded from the north east Pacific, was also found in False Bay and at Cape Hangklip during the course of this study. This genus has a germling which, during the initial phase of its growth resembles the germlings of both Ulva and Enteromorpha. Its further development differs however in that its monostromatic thallus becomes distromatic through cell division and not joining together of the monostromatic layers.