In the present study, the anaerobic treatability of automotive industry wastewater by using molasses, which is a sugar industry waste, as a co-substrate was investigated. The anaerobic treatment of automotive industry wastewater was examined at mesophilic temperature (37 degrees C) in a UASB reactor. The performance of the upflow sludge blanket reactor (UASB) was evaluated in terms of pH, chemical oxygen demand (COD), alkalinity and volatile fatty acid (VFA) parameters at 2-2.5 and 3.5 gCOD/L.d organic loading rates. The chemical oxygen demand (COD) removal rates for the UASB reactor were found to be 56-83%, 64-83% and 73-80%, respectively. The biogas yields were 0.34-0.50 L biogas/g COD removal, 0.33-0.46 L biogas/g COD removal and 0.31-0.46 L biogas/g COD removal, respectively. The application of the data obtained from the UASB reactor to the modified Stover-Kincannon and Monod kinetic models was performed, the U-max, K-B, K-S and U-max constants were determined, and it was concluded that the best model is the Stover-Kincannon model. Anaerobic sludge samples were taken after completing the experiments in the UASB reactor and prior to the start of the experiments. After drying the sludge taken and bringing it to small sizes, the SEM, and FTIR analyses were conducted.