Wastewater discharged from tannery industries is highly complex, concentrated, and toxic. In view of the varying nature of discharged wastewater and the numerous small industries in Egypt, there is a need for highly efficient treatment processes that are simple to operate and have low/reasonable construction and operation costs. This study investigated the possibility of applying innovative low cost biological treatment using upflow anaerobic sludge blanket (UASB) in providing adequate treatment for tannery wastewater. The anaerobic treatment application was thus evaluated through using two stage UASB reactors connecting in series, each with volume of 941. Five hydraulic retention times (HRT) were used along the experimental works, which lasted for a year, starting by HRT of 24 h then 18. 12,8 and finally 5 h for each UASB reactor. The proposed process at 12 h HRTs could pre-treat the tannery wastewater to be disposed to the municipality sewers. The study created best fit equations to predict the efficiency of the system. (C) 2011 Elsevier B.V. All rights reserved.