The 32 developmental mutants found in our laboratory have appeared in the course of the genetic analysis of adult Xenopus laevis issued from nuclear transfers, and of their progeny. These experiments originally were devised more than thirty years ago to test whether somatic nuclei had undergone irreversible changes during differentiation or whether they had remained totipotent. In the majority of cases, the mutations were carried by wild-caught imported frogs or their laboratory-bred progeny; however, the precise origin of several mutations has not been determined. The mutants have been subdivided into three classes: Maternal effect mutants. Three such mutants have been found; they affect the development of all the embryos from homozygous mothers independently of the genotype of the father. Developmental lethals. This class comprises 19 mutants, among which are included the previously called "autonomous lethals" caused by general metabolic defects that affect all parts of the embryos as well as the tissue- and organ-specific lethals, in several of which death occurs as a direct consequence of the anomalies. Developmental non-lethals. These are 10 mutants, suffering from specific defects not essential for survival. In addition, nucleolar mutants as well as mutants found in different species of Xenopus and mutants of Xenopus laevis found in other laboratories are also mentioned. The last part consists of an alphabetical description of the mutant phenotypes including more detailed analyses which have been carried out on several of them.