This is the first of a series of seven volumes that together are meant to present a fairly complete picture of our present knowledge of the fungi as experimental systems. In some ways the series is successor to a somewhat similar enterprise of some 25 years ago (The Fungi, four volumes edited by Ainsworth, Sparrow and Sussman). The present volume covers growth, differentiation and sexuality in 25 chapters. There is a good balance between the attention paid to yeasts and mycelial fungi, both ascomycetes and basidiomycetes. The level is quite good, so in fact the book offers 25 good review papers on related subjects. The volume editors have inserted cross-references to other chapters where appropriate, which enhances the coherence somewhat. The breadth of the coverage is satisfactory. In particular, the book is useful in bringing together recent results on various topics from different fungal systems. A good example is formed by the four chapters on mating type genes, so that we have here a nice overview of the results in yeast (Saccharomyces and Schizosaccharomyces), ascomycetes (Neurospora, Podospora and Cochliobolus) and basidiomycetes (Coprinus, Schizophyllum, Ustilago). The emphasis throughout the book is clearly on laboratory results, which is understandable since fungal research has been mainly a laboratory enterprise from the start. Nevertheless, I would have appreciated a chapter on what we know of growth and reproduction under natural conditions. We know a lot about a few model species that have a long tradition as laboratory fungi, and have little idea of variability within and between species. For example, we have very little information on (variation in) life cycles under natural conditions. Similarly, the relevance of phenomena like senescense and vegetative incompatibility under natural conditions is not clear. Perhaps in a later edition some space could be devoted to these aspects of fungal biology.