Pendant drop tensiometry has been employed to study the dynamics of adsorption of proteins (ovalbumin, b-casein, lysozyme, Hnl, and bovine serum albumin) and copolymers of L-glutamic acid at the heptane/water interface. We have characterized the dynamic adsorption behavior into three time regimes. An initial induction regime occurs where the surface pressure remains relatively constant, and proteins diffuse to the interface. Once a critical surface concentration is attained, the surface pressure increases sharply as the interface becomes saturated. Continuous loading of the surface occurs by diffusion and relaxation of proteins at the interface. In the third regime, a slow increase in surface pressure occurs as a result of protein conformational changes in the adsorbed layer. A novel TIRFS apparatus has been developed pins the liquid-liquid interface, permitting rate measurements and conformational changes to be determined over long periods. Using extrinsic fluorescent probes, adsorption dynamics have been be followed. Resonance energy transfer (RET) using double-labeled proteins is used to probe conformational changes in the adsorbed layer. A thin film surfaces forces device has been constructed to permit disjoining pressure isotherms of proteins solutions to be measured, and differences in the conformation of proteins at the interface observed.