Sulfur removal from a high-sulfur Turkish lignite (Gediz) using aqueous sodium hydroxide solutions having dissolved oxygen was investigated under mild oxidative conditions. Effects of the parameters such as sodium hydroxide / lignite weight ratio, temperature, and partial pressure of oxygen were investigated within the ranges of 0.05-0.8, 423-498 K and 1-2 MPa, respectively. Optimum values of these parameters were determined regarding sulfur removal and coal recovery. Influences of dry oxidation of the lignite sample as a preheatment at 573 K and subsequent washing of some treated lignite samples with 1 N HCl were investigated.