Chloroethylene oxide is the organic compound with the formula ClC<sub>2</sub>H<sub>3</sub>O. It is the epoxide of vinyl chloride. The compound is rarely observed, but it is widely proposed as a metabolite of vinyl chloride, formed by the action of cytochrome-P450. It is significant because it causes DNA alkylation. It isomerizes to chloroacetaldehyde, which modifies adenosine residues by conversion to 1,N<sup>6</sup>-ethenodeoxyadenosine (õdA).