Sixteen patients with typical and 17 with erosive ulcerative forms of lichen ruber planus were examined for the T- and B-immunity systems, myeloid series cells, complementary and spontaneous rosette-forming populations. B-lymphocyte levels were found elevated twofold in both groups of patients as against normal subjects. Patients with typical lichen planus developed a statistically significant elevation of T-lymphocyte count vs. normal subjects, whereas in patients with erosive ulcerative lichen planus this count was virtually unchanged. Reduced counts of active T-cells were detected in all the patients. The parameters of spontaneous and complementary rosette formation of neutrophils were different in the two groups of patients and in normal subjects. The counts of EAC-receptor carrying neutrophils were two times lower in the patients with erosive ulcerative lichen planus as against those with the typical form of the disease. Clinical manifestations correlated with changes in cell-mediated immunity factors; a marked defect of the neutrophilic receptor system has been detected, particularly manifest in erosive ulcerative lichen planus.