This study aims to investigate the removal of a reactive azo dye (Reactive Red 198) in anaerobic/aerobic sequencing batch reactors (SBR). The total volume of the SBR system used in the study was 10 I. Sludge age was selected as 15 days. The color removal efficiencies varied between 76 to 98% with initial color concentrations of about 20 and 50 mg l(-1). The effluent color concentration changed between 0.4-6.0 mg l(-1). The maximum dye removal efficiencies of the SBR system under 20 mg l(-1) dye concentration with 16/4 hours anaerobic/aerobic phases respectively were %98. The increase of anaerobic contact times had improved dye removal efficiency. The COD removal was also high during this period (81-94 %). The increase of organic loading rate from 500 to 1000 mg COD l(-1) day(-1) had improved the dye removal efficiency (from 88% to 96%) but deteriorated the COD removal efficiency to 81% from 88% in SBR systems.