NEW MATERIAL:The bis-dioxopiperazine derivative of formula I (R is alkyl, cycloalkyl, halogenated alkyl, carboxyalkyl, aryloxyalkyl, aralkkyl, arylalkenyl, aryl, heterocyclic group or alkoxy) or its salt.

EXAMPLE: 1,2-Bis(4-acetoxymethyl-3,5-dioxopiperazin-1-yl)-ethane.

USE: An antitumor agent. It has broad antitumor activity and metasasis-suppressing activity, high stability to a protonic polar solvent suitable for the drug preparation, and low toxicity.

PREPARATION: The compound of formula I is produced by reacting the novel compound of formula II with the reactive derivative of the compound of formula III. The novel compound of formula II can be obtained easily by reacting 1,2- bis(3,5-dioxopiperazin-1-yl)-ethane with formaldehyde.