A simple and sensitive color reaction of common epoxides as well as other some alkylating agents with 4-acetylpyrldine 2-benzothiazolylhydrazone (ABH) is described. These compounds gave a purpllsh red color after reaction with ABH for 2 hrs at 110°C in methyl cellosolve or for 20 min at 120°C followed by treatment with plperazlne on silica gel thin-layer plates. Four aliphatic terminal epoxides could be determined spectrophotometrically in the range from 20 to 125 nmol/ml. The limits of detection of these epoxides on silica gel thin-layer plates were 10 pmol/spot order by the visual inspection. The reaction mechanism is also discussed based on the chemical structure of the isolated chromophore.