Dendritic cells (DCs) are very potent antigen-presenting cells that play an essential role in the primary immune response to carcinoma. Tumor-infiltrating DCs have been found to be clinically significant in many human malignancies such as colon, stomach, lung, breast and hepatic carcinoma. However, clinical significance of activated and/or immature DCs in gallbladder carcinoma has not been reported yet. Thus, we immunohistochemically evaluated CD83+ DCs and CD1a+ DCs of cancerous and peritumoral area in 29 cases of resected gallbladder. In the results, CD83(+) DCs were significantly fewer in cancerous area than that in peritumoral area (1.55/hpf vs. 4.26/hpf, p=0.0047), but the numbers of CD1a(+) DCs did not differ (p=0.075). In addition, we defined a CD83 index as CD83(+) DCs/(CD83(+) DCs plus CD1a(+) DCs), and analyzed the relationship between CD83 index and clinicopathological factors. The group with a higher CD83 index (index >0.316) showed significantly better prognosis than the group with a lower CD83 index (index < or =0.316) in cancerous and peritumoral areas. In conclusion, we suggest the importance of tumor-infiltrating CD83(+) DCs as a useful prognostic factor for patients with gallbladder carcinoma.