An exhaustive, serious sourcebook on hazards of diagnostic x-rays--not something every family needs, but a valuable acquisition for libraries. Laws estimates that 30 percent of diagnostic x-rays are unnecessary, and the dangers are both financial and physical. (She excludes x-rays used as treatment, and hazards to workers, from this guide.) The total damage is reckoned at a wasteful expenditure of 3.75 billion dollars per year, and at least 1800 preventable cases of x-radiation-induced cancer. Among the causes: faulty x-ray units; nonradiologist physicians using their own machines (they use twice as many x-rays as physicians who refer their patients to radiologists); films that must be repeated because the operator used poor technique; unnecessary x-rays ordered to protect the physician legally; and unnecessary x-rays done against the physician's better judgment to pacify patients. The detailed advice here on avoiding unnecessary exposure is therefore very welcome. After Laws carefully sets out the risks, she discusses diagnostic alternatives and ""How to Minimize Your Exposure to X-rays"": first and foremost, discuss the risk-benefit question with the physician or dentist--and when x-rays are necessary be sure other body parts are properly shielded. Laws and the Public Citizen Health Research Group have done an altogether creditable job--both in establishing the dangers and in making them known to consumers, along with specific preventive measures.