The objective is to continue the maintenance of catalogs of autosomal dominant, autosomal recessive and X-linked phenotypes in man and to develop ways to enhance further their usefulness. These lists are intended to be exhaustive. Each entry, in so far as is known, refers to a single genetic locus. The entry consists of the preferred designation for the trait, a brief description of phenotype and genetic characteristics, and key references (particularly those with genetic information). The catalogs are maintained on the computer. Two classes of entries are maintained, those in which the particular mode of inheritance is quite certain and those in which it remains to be completely established (the latter being included for heuristic purposes). The catalogs are maintained by survey of the current periodical and monographic literature. The catalogs have usefulness in genetic counseling, differential diagnosis of genetic disorders and the evaluation of progress in the field of human genetics. Up-to-date information is maintained on the gene map of the human chromosomes. A Gene Map Newsletter is distributed quarterly to workers in the mapping field. Print-outs of complete computerized catalogs with indices are available at costs to anyone at any time. The catalogs are published periodically as a book. Four editions have appeared.