This paper describes an experimental evaluation of anaerobic digestion as a technological option for organic solid-waste treatment in the city of Bucaramanga (Santander, Colombia). The inoculum was selected by evaluating three different anaerobic sludges. Sludge from UASB No. 2 digestor at the Waste Water Treatment Plant in Rio Frio (Giron, Santander) was named [PTAR]. Sludge from the anaerobic biodigestor for pig manure treatment (Mesa de Los Santos, Santander) was named [PIG] a 1:1 sludge mixture of [PTAR] and [PIG] sludges was named [MIX]. These sludges' methanisation behaviour was evaluated in three different 500 ml capacity CSTR digesters at mesophyllic and thermophyllic temperatures. 25,20 and 18 day retention times were studied in a 20 1 CSTR digester having a 131 reaction volume. The results showed that raising the temperature from 10 oC to 15 oC above normal reactor temperature increased methane production by 3 times. It was also seen that retention time had a strong influence on specific methane production since the best conversions were registered at the longest time recorded (25 days) and it had a strong influence on DQO removal too. Another important condition for biodigestor optimal operation was agitation speed;this operation must be semi-continuous for maintaining methanisation process biological activity.