An isolate of Aspergillus niger was used as source of lipase which was purified to a specific activity of 729 U/mg, It has an acidic pH optimum and has a half-life of 42 h at pH 4.4, which can be increased to 138 h in tire presence of 10 mM calcium ions. For the first time a lipase from Aspergillus niger was characterised using the monomolecular film technique. The lipase wits classified to have sn-1 selectivity using diacylglycerols and R-isomer hydrolytic preference with pseudolipids representing triacylglycerols in which two of the ester bonds were replaced with ether and amide linkages.