The objective of the study was immunophenotypic analysis of mesenchymal stem cells from dog adipose tissue during in vitro cultivation. Materials and Methods: Mesenchymal stem cells were obtained from dog adipose tissue by explant method. The cells were cultured in CO2 incubator by standard procedure. Expression of cytoplasmic and membrane proteins on dog stem cells from fat tissue at the IVth and Xth passages was examined by immunohistochemical method using monoclonal antibodies. Determination the index of proliferationdogs adipose-derived stem cells (DADSCs) on IVth and Xth passages. Established that DADSCs contains multipotent stem cells, that are characterized by an almost homogenous fibroblast-like cells оn the IVth and Хth passages. It was difined, that fibroblast-like cells оn the IVth and Хth passages was expressed cytoplasmic and membrane proteins, which are specific to proliferating cells. Proliferation index in adipose-derived stem cells culture was significantly greater at the IVth passage – 1.90±0.02, compared to cells the Xth passage – 1,52±0,04 ** (P <0.01). DADSCs at the IVth passage are characterized by a maximum level of expression of pan cytokeratin – 299 ± 0.6, actin – 299 ± 0,58, vimentin – 265,7 ± 20,7, E-cadherin – 298,3 ± 1 points, indicating that this cells have a high adhesive properties, proliferation activity, cell signaling, interaction and mobility. The level of expression of these proteins remains high in the stem cells culture also at the Xth passage, although it is significantly lower in relation to the IVth passage. At the IVth passage adipose stem cells are characterized by average values of β-catenin expression – 97,7 ± 8,5 points, and low values of CD44 expression – 26,3 ± 3,1 points, which were significant decreased at the Xth passage of cultivation. The result of variance analysis revealed a significant effect of cell passaging on the level of expression of cytoplasmic and membrane proteins.