The lipid matrix of cell membranes is a natural binding site for amphipathic molecules. Consequently there are water-soluble, amphipathic peptides and proteins that exert their functions on membranes. Studies also showed that binding of amphipathic molecules (such as drugs) may change the functions of membrane proteins by altering the physical properties of the membrane. Thus, we want to understand how amphipathic molecules interact with membranes and find out the consequences of such membrane-molecule interactions. My thesis consists of development of new methods for studying the kinetics of molecular interactions with membranes and a series of comparative studies on different membrane-active molecules including peptides, proteins and drugs. My contribution to the methods for kinetics is to complement the equilibrium methods already developed in our lab for past twenty years. I established a micropipette aspiration system based on the system developed by Evan Evans in the 80's, but instead of measuring the elastic properties of membranes, we used it to study the dynamic interaction processes between amphipathic molecules and membranes.