A detailed geophysical investigation that included multibeam bathymetry, 3.5-kHz-channel and single-channel seismic profiles, 20 heat flow measurements and four piston cores was made of a mud volcano located about 8 km seaward of the toe of the Barbados Ridge Accretionary Complex in the northern Guiana Basin. The material erupted from the volcano covers an oval area about 3¿ km with its long axis oriented E-W, roughly perpendicular to the deformation front. A flat-topped mound on the western side of the feature is the currently active center. Acoustic stratigraphy suggests that mud volcanism began at the site about 200,000 Ma. A piston core taken on the flank of the active mound sampled deposits erupted 20,000--30,000 Ma that contain late Miocene nannofossils. Heat flow on the active mound is 4 times that in the surrounding basin. One-dimensional modeling of this anomaly supports a low-level continuing flux of mud and water at rates of 2--5 cm/yr. The mud volcanism appears to have arisen from the combined action of overpressured water that comes from beneath the accretionary prism and existing overpressures in the oceanic section. Large east-west trending basement escarpments underlie the two known mud volcanoes seaward of the Barbados Ridge Accretionary Complex, and they probably play an important role in developing vertical pathways for fluid to escape and in determining the location where mud volcanism starts. ¿ American Geophysical Union 1988