The formation and performance of granular sludge was studied in an 8l sequencing batch reactor (SBR) treating an abattoir (slaughterhouse) wastewater. Influent concentrations averaged 1,520 mg l(-1) volatile suspended solids (VSS), 7,685 mg l(-1) Chemical oxygen demand (COD), 1,057 mg l(-1) total kjeldahl nitrogen (TKN), 217 mg l(-1) total P. The COD loading was 2.6 kgm(-3)d(-1). The SBR was seeded with flocculating sludge from a SBR with an 1h settle time, but granules developed within 4 days by reducing the settle time to 2 min. The SBR cycle also had 120 min mixed (anaerobic) fill, 220 min aerated react, and 18 min draw/idle. The granules had a mean diameter of 1.7 mm, a specific gravity of 1.035, a density of 62 g VSS l(-1), a zone settling velocity (ZSV) of 51 mh(-1), and a sludge volume index (SVI) of 22 ml g(-1). Without optimizing process conditions, removal of COD and P were over 98%, and removal of N and VSS were over 97%. Nitrification and denitrification occurred simultaneously during react. The results indicate that conventional SBRs treating wastewaters with flocculating sludge can be converted to granular SBRs by reducing the settle time.