Clinical applications of monoclonal antibody for selective delivery of anticancer drug, toxin and radioisotope were reviewed. The difficulties in preparation and clinical application of chemoimmunoconjugate were pointed out. Also the difficulties of immunotoxin in clinical trial due to its high toxicity had been discussed and it is assumed that development of blocked ricin may overcome many problems related to toxicities. Clinically most advanced immunoconjugate seems to be radioimmunoconjugate. Among three types of immunoconjugates preparation of radioimmunoconjugate is easiest and some promising clinical trials were introduced in this review.