Two different extracellular lipases were produced by an anaerobic bacterium, Selenomonas lipolytica. A major lipase, lipase I, was isolated, which showed optimum activity at pH 6.0 and at $45^{circ}C$. It showed a molecular weight of 240 kDa and was a tetramer of a subunit having molecular weight of 60 kDa, which is different from the known bacterial lipases.