The performance of a 1 m(3) daily gas-production capacity, modified, Deenbandhu biogas plant was evaluated under hilly conditions. The modified plant had a digester volume of 2.65 m(3) with 55 days hydraulic retention time (HPT) as against a volume of 2.45 m(3) with 50.96 days HRT of the Action for Food Production (AFPRO) design. All the constructional items used in the modified plant were in accordance with the recommendations of AFPRO except the number of bricks, i.e. 625 in the modified design as against 800 in the AFPRO design. The rates of biogas production in October 1993 and January 1994 were 0.0357 and 0.0282 m(3)/kg feed (wet weight of dung); respectively. Thus the modified plant had a gas production efficiency of 70.5-89.4% of its rated capacity. All other functional parameters were within the optimum limits recommended for successful operation of any anaerobic digester.