The underlying idea that cancer is a genetic disease at the cellular level was postulated over 75 years ago when Boveri hypothesised that the malignant cell was one that had obtained an abnormal chromatin content. However, it has been only the last decade where enormous strides have been made toward understanding neoplastic development. Explosive growth in the discipline of cancer genetics is so rapid that any attempt to review this subject becomes rapidly outdated and continuous revisions are warranted. Conclusive evidence has been reached associating specific chromosomal abnormalities to various cancers. We have just begun to characterise the genes, which are involved in these consistent chromosomal rearrangements resulting in the elucidation of the mechanisms of neoplastic transformation at a molecular level. The identification of over 50 oncogenes has led to a better understanding of the physiological process. Tumor suppresser genes, which were discovered through inheritance mechanisms, have further shed some light towards understanding the loss of heterozygosity during carcinogenesis. The message emerging with increasing clarity concerning specific pathways which regulate the fundamental process of cell division and uncontrolled growth. The advances in molecular biology have led to a major insight in establishing precise diagnosis and treatment of many cancers resulting in prevention of death. The field is expanding so rapidly that a complete account of all aspects of genetics of cancer could not be accommodated within the scope of a single volume format. Nevertheless, a few very specific topics have been chosen, which readers may find of great interest in hopes that their interest may be rejuvenated concerning the bewildering nature of this deadly disease. The contributors to Volume 3 have provided up-to-date accounts of their fields of expertise. Although the contributors have kept their chapters brief, they include an extensive bibliography for those who wish to understand a particular topic in depth. For more than a century, cancer has been diagnosed on the enigmatic basis of morphological features. Establishing a diagnosis based on DNA, RNA, and proteins, which is done routinely now, was once inconceivable. Cloning a gene of hematopoietic origin is no longer a fantasy. The approach has shifted over the past 15 years from identification of chromosomal abnormalities toward zeroing in on cancer genes.