We surveyed and sampled two active and 3 inactive mud volcanoes on the Atlantic continental margin of Morocco. The active mud volcanoes (named Yuma and Ginsburg) are each about 4 km in diameter, rise between 150--250 meters above the seafloor and are the first active methane-related mud volcanoes to be identified in this region. The inactive volcanoes range in diameter from 1--3 km, with relief between 50 and 80 meters. Gravity cores from the crest of the active mud volcanoes yielded methane hydrates and mud breccia deposits. Chemosynthetic communities of Pogonophora worms and the bivalve Solemya were found on the surface of the active mud volcanoes. Sediment cores from the inactive volcanoes contained hemipelagic sediments, rich in foraminifera and ahermatypic coral debris, overlying mud breccia ¿ 2001 American Geophysical Union