A 450dm(3) pilot-scale upflow anaerobic sludge blanket (UASB) reactor was used for the treatment of a fermentation-based pharmaceutical wastewater. The UASB reactor performed well up to an organic loading rate (OLR) of 10.7kg COD m(-3) d(-1) at which point 94% COD removal efficiency was achieved. This high treatment efficiency did not continue, however and the UASB reactor was then operated at lower OLRs for the remainder of the study. Specific methanogenic activity (SMA) tests were, therefore, carried out to determine the potential loading capacity of the UASB reactor. For this purpose, the SMA tests were carried out at four different initial acetate concentrations, namely 500mg dm(-3), 1000mgdm(-3), 1500mgdm(-3) and 2000mgdm(-3) so that substrate limitation could not occur. The results showed that the sludge sample taken from the UASB reactor (OLR of 6.1kg COD m(-3) d(-1)) had a potential acetoclastic methane production (PMP) rate of 72 cm(3) CH4 g(-1) VSS d(-1). When the PMP rate was compared with the actual methane production rate (AMP) of 67cm(3) CH, g(-1) VSS d(-1) obtained from the UASB reactor, the AMP/PMP ratio was found to be 0.94 which ensured that the UASB reactor was operated using its maximum potential acetoclastic methanogenic capacity. In order to achieve higher OLRs with desired COD removal efficiencies it was recommended that the UASB reactor should be loaded with suitable OLRs pre-determined by SMA tests.