The lipase from strain BTL of Aspergillus niger was studied. The enzyme, which was mainly extracellular; was produced at elevated activity levels under optimum growth conditions. De novo biosynthesis of lipase occurred only in the presence of lipids and was completely repressed by glucose and glycerol. The reaction products, oleic acid and glycerol, showed differed inhibition patterns during triolein hydrolysis. The enzyme exhibited high specificity towards middle chain triglycerides and was possibly activated by double bonds in the fatty acid chain. It exhibited a marked stability against organic solvents.