Abstract: Objective To investigate the phenotype, number and distribution of inflammatory cells in early and late stages of spontaneous regression of halo nevi, and to elucidate the immunological mechanisms for spontaneous regression of these nevi. Methods Halo nevi, their surrounding non-lesional skin, and normal control skin were examined by immunohistochemical staining with monoclonal antibodies to CD3, CD4, CD8, CD20, CD1a, CD56 and CD68. Staining results were observed and analyzed by the computer image analysis system, image-pro plus 6.0. Results The number of CD4+, CD8+, CD20+, CD1a+ cells, along with the diameter of CD1a+ and CD68+ cells was significantly increased in the lesions of early and late stage of spontaneous regression of halo nevi than in non-lesional skin and normal control skin（both P < 0.01）. The ratio of CD8+/CD4+ cells in the lesions of late stage of spontaneous regression was also higher than that in the lesions of early stage（2.05 ∶ 1 vs 1.82 ∶ 1）. A massive infiltrate of CD8+ cells was observed in the nests of nevus cells. Conclusions CD4, CD8, CD20, CD1a, CD56 and CD68 positive cells are all involved in the spontaneous regression of halo nevi, and CD8+ cells may play a predominant role in this process.