Abstract
In this paper we present the main methodological principles of planning and performing case-control studies. We also present the methods of statistical analysis of data obtained in case-control studies. Main advantages and disadvantages, clinical and public health applications of case-control study design are described. We provide practical step-by-step instructions on sample size calculation using "EpiInfoTM" software and free online calculators, calculations and interpretation of adds ratios as well as on calculations of Pearson's chi-squared and McNemar test using examples from real studies. Examples of case-control studies from the literature including one example from the Arkhangelsk region are also presented.