This scientific opinion of EFSA deals with the risk assessment of the monomer 1,3-bis(isocyanatomethyl) benzene, CAS No. 3634–83-1, FCM Substance No 988. In water and gastric fluid simulant, immediate and complete hydrolysis of the substance to 1,3-benzenedimethanamine occurs. The toxicity of 1,3-bis(isocyanatomethyl)benzene was tested in three in vitro genotoxicity tests, with and without metabolic activation and in an in vivo micronucleus assay in rats and was considered as non-genotoxic in vivo. In addition, its hydrolysis product, 1,3-benzenedimethanamine, was tested in two in vitro tests, in the presence and absence of a metabolising system, and one in vivo mouse micronucleus assay. The tests were negative. No concern for genotoxicity in vivo is raised by 1,3-bis(isocyanatomethyl)benzene and its hydrolysis product 1,3-benzenedimethanamine. The CEF Panel concluded that that the use of the substance 1,3-bis(isocyanatomethyl)benzene as co-monomer in the manufacture of a middle layer coating in a multilayer film does not raise safety concern if the migration of its hydrolysis product, 1,3-benzenedimethanamine, does not exceed 0.05 mg/kg food.