The article is of interest to health professionals operating in the system of the Ministry of defense of Ukraine and Armed Forces of Ukraine and other state authorities, institutions and non-government organizations. Also, the results of the study will be useful to the representatives of the medical service, as service is a direct participant in the process of evaluating the effectiveness of the military personnel's medical examination system. The place and role of the clinical examination of personnel in the health care system have been established. This has allowed to identify the internal and external factors in the context of the issues of this article. Internal and external factors were investigated in the context of managed and unmanaged factors. The paper presents a mathematical model of the medical care for servicemen who undergo medical examinations with using a semi-Markov random process. A quantitative criterion for the effectiveness of health care, called the employability ratio, is proposed. To establish the dependence of the employability ratio on the model parameters, an exponential law of time distribution between diseases was used. Such a law can be considered as a characteristic of the military personnel of a relatively young age. The results of this study are the starting point for solving the scientific task of substantiating the scientific and methodological apparatus for assessing the effectiveness of the prophylactic medical examination in the system of medical support of servicemen of the Ministry of defense of Ukraine and Armed Forces of Ukraine. In further studies will be shown the dependence of the employability ratio on the model parameters, as well as the cost of staying a serviceman in a healthy condition.