The use of the dynamic pendant drop method has permitted the accumulation of information in real time on the kinetic and theological processes that accompany the adsorption of bovine serum albumin (BSA) at the dichloromethane (DCM)/water interface in the presence and in the absence of poly(D,L-lactide) (PLA50). These results have been compared with those obtained at the air/water interface. The study of the adsorption kinetics of BSA at the DCM/water and air/water interfaces has shown that the adsorption process was diffusion controlled in both cases for relatively low concentrations of protein (0.005 g/L) In the presence of PLA50, the adsorption of BSA at the DCM/water interface led to a mixed interfacial layer. The mechanism of the formation of this mixed interface involves the penetration of BSA into the saturated layer of PLA50 with the displacement and condensation of the PLA50 segments. In all cases, theological results indicated a pure elastic behavior for the mixed BSA/PLA50 interfacial layers. The absence of relaxation upon the application of dilatational stress was attributed to the instantaneous displacement of the PLA50 segments and the nonexpulsion of the BSA segments. These results are interpreted with respect to the preparation of biodegradable PLA50 microparticles related to an emulsion-based process.