The inhibition effects of heavy metals (Cu, Ni, Zn, Pb) on to anaerobic sludge were investigated using glucose (3000 mg/l COD) as carbon source and electron donor with a batch experiments (serum bottle assays). The seed sludge was obtained from a UASB (upflow anaerobic sludge blanket) reactor treating yeast wastewater of the Pakmaya Yeast Factory in Izmit, Turkey. The heavy metal concentrations tested were copper (1-1000 mgCu/l), nickel (1-3000 mgNi/l), zinc (1-1000 mgZn/l, and lead (1-10,000 mgPb/l). According to relative inhibition effects of heavy metals on methane producing activity of anaerobic sludge and COD removal in serum bottles experiments during incubation time (12 d) were Cu(most toxic) > Ni similar to Zn > Pb(least toxic). In general, cumulative methane production (ml) decreased with increasing heavy metal concentrations above 10 mg/l. Inhibition effects of heavy metal values (1-10 mg/l) were low on COD removal. Heavy metals measurements in influent and effluent of serum bottles were also compared. Effluent heavy metal concentrations from low to high were found to be Pb, Cu, Zn and Ni.