Bisacetoacetamides were prepared, and their polymerization was investigated. The acetoacetyl groups were introduced to diamines by the reaction with diketene to give bisacetoacetamides.They were polymerized under high pressure (34.5 MPa) at 200 degreesC for 30 min to create the crosslinked films. The polymerization mechanism was studied by a model reaction of acetoacetanilide. The model-reaction results indicated that the polymerization of bisacetoacetamides proceeded by addition reactions of the isocyanates formed as intermediates and in part by condensation reactions between the acetoacetamido groups. The isocyanates also reacted with the urea groups on the polymer chains to form biurets, which mould cause crosslinking. In the presence of a diamine, the reaction produced a soluble oligourea.