In situ AFM images of phospholipase A₂ (PLA₂) hydrolysis of mica-supported one- and two-component lipid bilayers are presented. For one-component DPPC bilayers an enhanced enzymatic activity is observed towards preexisting defects in the bilayer. Phase separation is observed in two-component DMPC-DSPC bilayers and a remarkable enhanced hydrolytic activity of the PLA₂-enzyme for the DMPC-rich phase is seen. Furthermore, in a supported double bilayer system a characteristic ripple structure, most likely related to the formation of the P_β'-ripple phase is observed.