Biogas production was measured on several anaerobic lagoons. Biogas production rates varied widely (0·02 to 0·50 m3 m−2 day−1 (lagoon surface area basis): 0·03 to 0·23 m3 m−3 day−1 (lagoon volume basis)). Carbon dioxide concentration of the lagoon biogas was less than 35%. Biogas production was influenced by lagoon organic acid concentration, position of the collection cover on the lagoon surface and lagoon temperature. Biogas production from normally-loaded lagoons (