The exact prevalence of primary immunodeficiency (PID) in the population is unknown. It is estimated as 1 per 10,000 excluding the IgA asymptomatic selective deficiency. Thanks to the effective protocols of immunological and genetic diagnosis introduction, the number of patients diagnosed primary immunodeficiency is growing every year both worldwide and in the Republic of Belarus. Currently, 525 PID patients have been registered in Belarus. These data are comparable with the countries of Eastern Europe. To confirm the PID diagnosis, methods of immunological and genetic diagnosis have been used as a rule. In the Republic of Belarus, 54.5% of the total number of detected PID patients have been verified genetically. This indicator is comparable with the Germany and the USA data. Among the causes of PID patients deaths in Belarus as well as in the world, infectious complications are at the first place, the second place is occupied by cancer.