Immunohistochemical technique (ABC method) was applied by using anti-S-100+ protein and anti-lysozyme antibodies to examine the local infiltration of dendritic cells (DC) and lysozyme positive (lys+) cells in 78 cases of transitional cell carcinoma of the bladder. 64 of the 78 cases were followed up. The results showed that DC were present in all carcinoma nests and stroma, being more numerous in the stroma than in the parenchyma. The number of DC was positively related to 5-year survival rate, which, in B group was significantly different from that in A group (P less than 0.05). It is also related to the degree of differentiation, the highly differentiated cases having larger number of DC than the moderately or lowly differentiated cases (P less than 0.01). There were more DC in the non-infiltrated muscle layers than in the infiltrated muscle layers. (P less than 0.01). This suggests that DC might participate in the anti-tumor immune reaction of the body, the intensity of which is related to the number and distribution of DC in the carcinomatous tissue. This may provide a reliable basis for evaluating the prognosis and choosing the operation methods, especially in recurrent carcinoma of the bladder.