Human hybridomas were generated through the fusion of the human B-lymphoblastoid cell line HO-323 with the regional lymph node lymphocytes of colonic cancer patients who had received a local immunotherapy. A total of 353 hybridomas were obtained from 4 patients and 116 of these were found to secrete greater than or equal to 100 ng/ml human immunoglobulin. The efficiency was remarkably high as compared with that from patients without the local immunotherapy. Further immunohistological examination showed that 5 hybridomas secreted IgM which selectively reacted with colonic cancers. The results indicate that local immunotherapy could be an adjunctive tool for the generation of highly potent human hybridomas through augmenting the host's immunity.