Recent work by others and preliminary data from this department have suggested that farmers are at greater risk for cancer that had been generally recognized. Using the Iowa agricultural population as a base, further exploration will include: 1) improvement in rate and quality of occupational recording. This will be done by linkage with drivers' license tapes, direct mail questionnaires, and completion of death certificate coding; b) both proportionate and standardized incidence and mortality rates will then be calculated for all cancers by main occupational groups. Inferences on type of farming practice will be derived by geographic analysis of crop areas by cancer incidence and mortality; c) finally a case-control study of specific farming practice risk factors will be done for cancer of the prostate. Cases will be farmers with cancer of the prostate and controls will be farmers without prostate cancer from 2 sources; neighbor and statewide randoms.