Statistics for The present study deals with the treatment of weak domestic wastewater in UASB(up flow anaerobic sludge blanket) reactor system. An experimental reactor, made of PVC tubes, 24 litre capacity was used for the experiment to evaluate the performance of the reactor. The HRT(hydraulic retention time) was maintained as 3 days. The study was carried out for a period of 40 days. The results of the experiment indicate that the anaerobic treatment of domestic wastewater in UASB reactor is a promising technique for tropical countries. © Enviromedia.