Introduction

New data on human gene mapping accumulate rapidly as a result of the genetic analysis of somatic cell hybrids, the application of in situ DNA-DNA and DNA-RNA hybridization, and the detection of new polymor phisms which can be followed in family studies.It is the aim of these international workshops on human gene mapping to review the progress in this field on a yearly basis.These meetings facilitate the integration of data obtained by the different techniques and in different laboratories.The current status of the human gene map, as was discussed in the plenary session of the Rotterdam Conference, is presented in the different committee reports, which form the first part of these proceedings.New information relevant to gene linkage is presented as short reports in the second part of this volume.To emphasize the special character of the committee reports, they are now published as one entity with a joint reference list.The reader interested in mapping data on a particular chromosome finds his entry in the committee reports on chromosomes 1 and 2, the other autosomes, and the X chromosome.Linkage data relevant to a particular gene marker can be found by first consulting the 1974 listing of gene markers included in this volume.If available, the chromosome assignment will be indicated in the same list.Further information on the assignment can then be found in the committee reports.