This volume, the first of its kind ever, is designed to provide both laypersons and professionals with a detailed description of the occurrence of each common form of cancer in the ethnically, socially, and environmentally complex milieu of a modern urban complex. The place is Los Angeles County, and the patterns of 72 different malignancies are described according to race, age, sex, social class calendar time (since 1972) and most notably, individual neighborhood, using detailed maps of high risk. The book permits residents to screen the malignancies and identify those of special concern locally, and to identify other communities with similar concerns. The pattern of each malignancy is briefly discussed with reference to background knowledge of causation and the degree to which the observed pattern was expected on that basis. Persons residing outside Los Angeles County will identify patterns likely to prevail in their own communities. Physicians and scientific investigators in California and elsewhere can use the material provided to counsel patients and evaluate the consistency of any specific pattern of occurrence with each specific causal hypothesis. There is a detailed appendix that describes the source of data, provides the basis for the choices made in the production of the volume, and gives a perspective on the search for 'clusters' of malignancy. This title compares different types of cancers with respect to the degree of non-random occurrence. It contains numerous maps detailing the demographic and geographic pattern of cancer occurrence in Los Angeles County. It provides an empirical perspective to the search for disease 'clusters'.