A systematic account of the marine gammaridean and caprellid Amphipoda of the Cape Province of South Africa west of Cape Agulhas (20°E) is provided. The analysis is based on collections totalling over 70 000 specimens in the possession of the University of Cape Town and of the South African Museum, as well as records from the existing literature. Two hundred and thirty-two species are recognized from the area. These include fourteen species which are recorded for the first time from southern Africa, as well as the following eleven species which are described as new to science: Panoploea stegosaura, Maera emarginata, Maera komma, Maera thrixa, Melita mucronata, Listriella saldanha, Socarnes septimus, Perioculodes pallidus, Heterophoxus cephalodens, Heterophoxus opus and Podocerus pyurae. In addition the following changes in taxonomy are proposed: A new family-the Temnophliidae-is erected for Temnophlias K. H. Barnard, 1940. Ceradocus aviceps K. H. Barnard, 1940 is removed to Quadrivisio. Tryphosella africana K. H. Barnard, 1955 is synonymized with Hippomedon longimanus. Tryphosella normalis K. H. Barnard, 1955 is removed to Hippomedon and H. rotundipleura Ledoyer, 1973 synonymized with it. Microlysias indica K. H. Barnard, 1937 is synonymized with M. xenoceras. Uristes induratus K. H. Barnard, 1925, is removed to Procyphocaris where P. primata J. L. Barnard, 1961 falls into synonymy with it. Podocerus cristatus of K. H. Barnard (1916) and Griffiths (1973, 1974a, c) is referred to P. inconspicuus. Allorchestes inquirendus is synonymized with Hyale grandicornis, Talorchestia inaequalipes with Orchestia gammarella and Caprella falsa with C. penantis.