Large-cell anaplastic malignant lymphoma of T-type (T-LCAL) as an original form among human non-Hodgkin's malignant lymphomas in Updated Kiel Classification (1988) was defined. In human pathology T-LCAL presents a considerable diagnostic difficulties and is not associated with HTLV except some cutaneous forms. Comparative examination was carried out in 5 cases of baboon T-LCAL as a part of long-term investigation of the lymphoma outbreak in Sukhumi monkey stock. In tumor-bearing baboons routine morphological methods, immuno-morphological phenotyping of lymphoma cells with panel of MoAT and polyclonal antibodies to T- and B-lymphoid cell antigens and antigens of cell activation, including CD30 antigen, in cell suspension and on cryostate sections were used. STLV-provirus integration in DNA of lymphoma cells in PCR was determined. Diagnostically important morphological features of baboon and human T-LCAL include pronounced anaplasia and anisocytosis of CD30-positive large blast cells, tumour cell tendency to infiltrate sinuses and vascular walls. The presence of T-cell markers (CD2, CD3, CD4, CD8 in our cases) and antigens of cell activation (CD25, HLA-DR) were found. In DNA of baboon lymph node lymphomas (also in the cases without skin involvement) env- and tax-fragments of STLV-1 provirus were detected.