Abstract: The antitumour compound ICRF 154 was orally effective against a number ofexperimental tumours. It showed neither activity nor toxicity in a preliminaryclinical trial. We also found it useful in the treatment of psoriasis ~(14)C-labelled ICRF 154 was synthesized (for absorption, distribution andexcretion studies) in three steps, using (carboxy-~(14)C) carboxylic acid as thelabelled starting material. The radiochemical purity was 99.8%, as determinated by thin-laryer radio-chromatography; and specific activity, 3 Ci/mol. Radiochemical yield was 30%.