The hydrolysis of several esters catalyzed by lipase of Candida rugosa was used to analyse the interaction between the ester substrate and the active site and the geometry and steric restrictions of ’alk’, ’ar’ and ’h’ subsites. Using 4-R-C6H4-CH(R’)-COOEt and ethyl trans-cinnamate, the presence of a low electronic density zone in the `ar’ pocket is described, the dimensions of the pocket produced by Phe-296 and Leu-297 in the `alk’ subsite and the size of the ’h’ subsite are described.