The scope and objectives of this work are as follows: (1) To determine the effect of pressure on interfacial tension in systems that are relevant to tertiary oil recovery. (2) To investigate the effect of pressure on the phase behavior of such systems. Both of these questions have a connection with mass transfer and dynamic liquid-liquid interfacial tension. (3) To investigate the nature of the microemulsion phase, and the occurrence, properties and behavior of microemulsions in general. (4) One objective that was not originally stated for the work was to elucidate an anomalous sedimentation effect that was discovered in the course of the study. This report is submitted in two subdivisions. These comprise, first (Part III of the report) 4 abstracts of the work of Dr. M.V. Ostrovsky, on microemulsions per se and the effect of pressure and time on interfacial tension. The second subdivision (Part IV of the report) consists of the work of Mr. Chan, Miss Chen and Miss Broers, on the effect of pressure on phase equilibria, and on the discovery of an anomalously rapid rate of sedimentation in microemulsions. Abstracts of their theses are presented. In addition, abstracts of two papers on anomalous sedimentation in systems containing microemulsions are presented.