The potential energy surface for the reaction of O( 3 P) with HCNO (fulminic acid) has been studied using ab initio methods. Critical points were optimized at the DFT-B3LYP/6-311++G(d,p) level of theory, combined with single point energy calculations at the CCSD(T)/6-311++G(d,p) level. Two key critical points were re-optimized at the CCSD(T)/6-31G(d,p) level, showing a slight entrance barrier for the reaction. The energetically accessible reaction paths from an HC(O)NO complex lead to H+CO+NO and HCO+NO products. The calculations are in qualitative agreement with previous experimental results.