The paper is dedicated to methods of determination of sample size for population incidence study. An analysis of incidence including urological incidence is necessary condition for achievement of high level population health, for intensive health care service development, for control of medical and preventive treatment facility function and management thereof. Determination of true prevalence rate of urological diseases needs for evaluation of so called hidden urological prevalence. To resolve this task focused population examination is more informative contrary to analysis of medical aid appealability. However especial population examinations in general are labor-consuming and associated with signifi cant time and resources expenses. In particular it concerns total survey. For this reason sampling examinations as an optimal variant of true prevalence evaluation are used frequently. One of the essential constituent and at the same time one of stages of sampling population examination undertaken for incidence determination is sample volume (size) estimation. Correct estimation of necessary case number for sampling incidence examination performing substantially provides objectivity of the data obtained and determines requirement for facilities and resources for its realization. An equation is provided for sample size computing in case of simple random selection wherein frequency of studied attribute in population (for example, urological incidence) and frequency of alternative attribute are considered. Literature review about urological prevalence study and methods of sample size determination is presented.