The Ana Yatak massive sulfide deposit is located in the Ergani-Maden District of south-eastern Turkey and has been a major source of copper for more than 4,000 years. The mineralization is hosted by strongly chloritized serpentinite, gabbro, diabase, and mudstone. The ore body is similar to 600 x 250 m in maximum dimension, mainly consists of pyrite and chalcopyrite, and locally contains abundant magnetite, pyrrhotite, and chromite. The gangue contains predominantly chlorite, rarely quartz. This paper is mainly concerned with an investigation of the sulfur-isotope systematics of the Ana Yatak deposit.