Phase transfer catalysis is a term characterizing an essential advance in chemical synthesis techniques over the last decade. Several review articles have already appeared"', and now we have the first two monographs (there is already a publisher's announcement of a third'"'). They are written by authors who have taken active part in the development of the technique, Starks even coining the term "phase transfer catalysis". The books have been conceived and printed in a pleasantly readable manner, and the number of printing errors has been kept within limits. Both books have been slightly inflated by the repetition of the same subject matter in several chapters and by the tabulation of every compound treated. together with yields, which seems unnecessary in the case of homologous or analogous series with little difference between the individual members. In each book the material in the synthesis section is arranged by the type of reaction: simple substitutions, alkylations and condensations, methods for carbene production, ylide reactions, oxidations and reductions, miscellaneous further phase transfer catalysis reactions ((hi\ i h the arrangement in Starks and Liotta). Efforts have been made to cover the literature as comprehensively as possible. Weber and Gokel cover it to the end of 1976, and there is an appendix with further references from 1976-77, arranged by chapter, giving a total of 650 references. Starks and Liotta cover just 700 of the 900 references known to them to the end of 1977. The field is developing rapidly; for the period 1978-79, the present reviewer already has more than 200 new references in his file! There are marked differences in the way that the two books deal with the theoretical foundations (Starks and Liotta take three chapters with 90 pages, Weber and Gokel one chapter with 17 pages), and in their printing of typical preparative details (lacking in the case of Weber and Gokel). While Weber and Gokel deal briefly with general, mechanistic, and theoreticalproblems, StarksandLiotrahaveputalotofeffortinto collecting data on the extraction of anions and cations into organic solvents, on the reactive behavior in different media, and on other fundamental questions. Kinetics, limiting conditions, and possible mechanistic alternatives are discussed, and hints are given on the choice of the catalyst and the solvent and also of the conditions for a new reaction. Weber and Gokel d o give all this material as well, but in a very summary form. Although we are still far from being able to predict the catalyst activity or the exact course of a new phase transfer catalysis process, Starks and Liotta give the essential starting points for a general theory, and in the case of substitution reactions a fair amount of progress has been made. Difficulties arise in the explanation of alkylation and carbene production in the presence of concentrated caustic soda. Starks and Liotta's critical approach, which is otherwise impeccable, breaks down here, for example, in the use of different values for the selective extraction of OH ~ (p. 173: B r -is 10' times more readily extracted than O H -, in Table 7, p. 24, however, it is only 1650 times. Although in