Panniculitis is a heterogeneous group of diseases that are characterized by a subcutaneous adipose tissue (SAT) lesion and frequently occur with involvement of the musculoskeletal system and viscera in the process. This is a chronic multiple organ disease. The gold standard for its diagnosis is noted to be a morphological study. The paper presents the current classification of panniculitis. Objective — to study the morphological features of idiopathic lobular panniculitis (ILP) in accordance with the nature of the course and clinical forms of the disease. Subject and methods. Biopsy specimens were studied in 62 patients with various clinical forms of ILP. Biopsy and surgical materials were investigated by light optical morphological methods. The results were statistically processed using a statistical analysis software Statistica Version 10 package for Windows («StatSoft Inc.», USA). The differences were considered statistically significant at an error level of p<0.05. Methods, such as Pearson’s c2 test (analysis of contingency tables), Student’s t-test, Z-test for comparison of proportions, nonparametric tests, such as Mann—Whitney U-test, Kruskal—Wallis test, were used to assess the results. Results. The nature of the morphological parameters of the disease corresponded to the course of ILP. The acute course of the disease was characterized by the predominance of liponecrosis and inflammation concurrent with productive-destructive vasculitis. In the chronic course, there was a preponderance of lymphohistiocytic infiltrate with gigantic macrophages (lipophages) and granuloma-like structures. The above morphological changes were characteristic of the phagocytic morphological stage of node formation. The fibroplastic stage of panniculitis was absent in this study. The morphological features of the disease were shown depending on the form of idiopathic lobular panniculitis, which may be of diagnostic value in the differential diagnosis of panniculitis. Conclusion. The pathologist must first of all pay attention to the preferential localization of pathological changes (in the SAT septa or slices), the presence or absence of vasculitis and the nature of the infiltrate. The skin in panniculitis is typically intact or has minimal changes following the pattern seen in reactive ones. Panniculitis shows an undulatory course, and therefore all signs of this disease are present in biopsy specimens; however, morphological signs of the acute inflammatory, lipophagic or fibroplastic stage of the disease predominate depending on the stage and activity of the process.