Introduction. Patients with diseases of the circulatory system are under long-term follow-up and monitoring of a primary care physician and, if their condition is stable, receive standard therapy. However, in the absence of exacerbations, the physician does not always detect the need for laboratory tests, which often must be performed regardless of the patient's condition. In this regard, it seems relevant to investigate the organization of laboratory examination of dispensary patients in accordance with the requirements of valid clinical guidelines. The aim of the study is to analyze the practice of laboratory tests ordering in follow-up and monitoring of patients with cardiovascular diseases. Materials and methods. A peer review of the laboratory examination of patients with circulatory system diseases under follow-up and monitoring in 2022 was carried out in three medical organizations providing primary healthcare within the territorial compulsory health insurance program in St. Petersburg. The compliance of the ordered laboratory tests with the requirements of valid clinical guidelines was determined. Results. It was found that laboratory examination of patients often deviated from the requirements of clinical guidelines, not ensuring the necessary completeness of diagnostics. At the same time, the completeness of the examination was significantly associated with the patient's diagnosis, the specialty of the physician who carried out follow-up and monitoring, as well as the features of the laboratory examination and follow-up organization. There were differences in the frequency and number of the laboratory tests ordered to patients during the year. There was a replacement of tests specified in clinical recommendations with other ones that did not meet the objectives of follow-up and monitoring. Discussion. The analysis of laboratory prescriptions demonstrated more successful work of physicians in managing patients with common diseases. In case of rarer pathologies, doctors' commitment to following recommendations is significantly lower. The clinical recommendations themselves, which are not always sufficiently detailed in the case of the laboratory examination, can contribute to the variability too. Besides, the identified variability could be associated with differences in the tests' titles and the approach to their appointment in different medical organizations. In addition, the results of our study indicate the importance of a proactive approach in working with dispensary patients. At the same time, the centralization of laboratory tests does not reduce the availability of the tests. Conclusions. Peer review has shown that patients with the same diagnosis are often prescribed different types and quantities of tests with different frequency. The differences revealed allow to objectively state that physicians have different approaches to the selection of tests. As a result, the clinical pathways of patients with similar clinical conditions may differ significantly, and the distribution of resources among patients in need may not correspond to the optimal one. This requires the active practical application of clinical guidelines and the development of a proactive follow-up and monitoring system.