During the FAMEX cruise of the R/V L'Atalante (April 2002), swath bathymetry and seismic profiles were recorded along the Baja California margin from 23¿ to 27¿N. The upper-slope of the margin exhibits active faulting of recent sediments along the Tosco-Abreojos fault system (TAFS). Flower structures evidence strike-slip motion along the TAFS. Right lateral strike slip faulting, associated in places with small extensional features, are consistent with present-day slip and extension rates predicted along the TAFS. The TAFS thus belongs to the western active boundary of a Baja California Block yet not totally transferred to the Pacific plate.