The purpose of this book-the fourth volume of a series on Can cer Markers-is intended to provide an updated "status report" on today's use of cancer markers in the diagnosis and monitoring of can cer, with an emphasis on cancer markers detected in the serum. It has been 7 years since the publication of the last volume in this series. The 1980, 1982, and 1985 volumes covered the development of cancer markers, not only in their roles of unraveling the basic biology of can cer, but also as increasingly important players in the management of patients with cancer. During the last 7 years we have seen the applica tion of a number of markers identified by monoclonal antibodies, as well as the beginnings of the use of genetic markers defined by mo lecular probes. Measurements of oncogenes in tissues or cells prom ise many applications for the future, but as yet, these genes have not shown to be useful as serum markers of cancer. The commercial interest in serum markers for cancer, particu larly for the diagnosis and monitoring of tumor patients, is indicated in Chapter 24 by Owen, where the total worldwide market for cancer markers is projected to increase from $148 million in 1988 to $232 million in 1993. The degree of research interest in cancer markers is reflected in the fact that in 1988 a separate category for tumor mark ers was added to Index Medicus.