It is several quantum jumps from Amram Scheinfeld's classic You and Heredity to Know Your Genes. Time was when virtually all you could say about potential offspring was something about blood groups, eye color, hemophilia, or a few other well-known genetic traits. The successes of molecular genetics and cell biology have changed that picture radically. Today it is possible to identify carriers of many heritable diseases and to culture fetal cells in order to determine chromosomal abnormalities or particular biochemical deficiencies. It is possible to treat Rh disease or phenylketonuria, and a couple can elect to abort a Down's syndrome or Tay-Sachs fetus. Possible, yes, but not without the cooperation or enlightenment of parents. Milunsky is a medical geneticist and counselor out to enlighten. He begins with a discussion of the mechanisms of inheritance, distinguishing dominant from recessive inheritance, polygenetic traits, sex-linked or sex-limited disorders. He describes the state of the art--amniocentesis, carrier-testing, treatment of disease in utero--as well as future possibilities. He deals with such contriversial issues as the extra Y chromosome associated with criminality in males, the ethics of experimenting with abortuses or of euthanasia for infants born with major defects. Some of this makes for depressing but no less important reading. Milunsky does not believe in arbitrary Death Committees or government-imposed rules; rather, each case must be judged individually. He also emphasizes that the role of the genetics counselor should be to convey information and not dictate action. On occasion, Milunsky's remarks about the association of a disease with poverty or illegitimacy-without a follow-up--leave the reader wondering what he means. These are exceptional, however. The book stands as a rich and valuable source to be recommended to all adults--potential parents or not.