Seismic reflection profiles and magnetic intensity measurements were made on the continental shelf and upper slope between Cape Rhir and Cape Sim, Morocco. Patterns of shelf and regional structures imply a downfaulted origin for this continental margin, modified by later Atlas orogenic movements. Regional folding of the Western Atlas Mountains extends seaward of the shelf edge, truncated by the present shelf and slope surface. A buried early Miocene(?) folded unconformity truncating underlying folds indicates that at least two phases of folding have affected the area, probably during Oligocene and Miocene times. The magnetic survey indicates an east-west basement fault or flexure below Cape Tafelny, and suggests the extension below the continental shelf of a basement upli t under the Western Atlas Mountains. Evidence of diapirism suggests the continuation below the continental shelf of Triassic evaporites found in the adjacent Essaouira basin.