This review covers, essentially, material published in the years 1960 and 1961. For reasons of space, work on plant cells, physicochemical studies on inanimate membranes, and most of the work on electrophysiology (even if it touched transport problems) had to be excluded. A number of symposia were held dealing wholly or partly with transport problems (25, 112, 173, 256, 282) and several surveys were published (43, 82, 242, 331, 333, 338a). Some reviews of more restricted scope will be mentioned below. A number of con­ tributions to the symposia mentioned (particularly 173) also have the charac­ ter of reviews. Developments of special interest, in the opinion of the reviewer, include the growing amount of valuable information gained from bacteria (especially from studies on permease systems for which mutants lacking enzymes or perm eases are especially favorable), the increasing evidence for the operation of carrier systems, the approach towards better understanding of the alkali cation transport based on the study of membrane ATPase, and the growing knowledge about the types of functional membrane polarity in transporting cells, mainly of epithelia.