Selective intra-arterial infusion of ethylcellulose microcapsules containing mitomycin exerts its therapeutic effects through infarction and sustained drug action—ie, chemoembolization. Sixty primary or secondary carcinomas in the kidney, liver, urinary bladder, prostate, cervix, vagina, sigmoid colon, Douglas' pouch, and bone were treated with single or repeated chemoembolizations using microcapsules delivered through percutaneous catheterization as a preoperative or palliative measure. Substantial tumor reduction of greater than 30% in measurable maximum diameter was found in 65% of the tumors; pain relief occurred in 80% and hemostasis in 100%. Preoperative chemoembolization remarkably facilitated radical surgery in 18 (82%) of 22 patients. The summed response rate was 77%. Systemic toxic effects were mild, and all patients tolerated the treatment. Though the follow-up periods are less than two years, 37 patients are alive with or without tumor.