The reaction between an enolate carbanion and
m
‐dinitrobenzene (
m
‐DNB) has been reported by Janovsky and Erb and it is Zimmermann who initially applied the specific reaction between
m
‐dinitrobenzene and 17‐
oxo
‐steroids (or 17‐
keto
‐steroids) in the presence of an alkali to the field of ketosteroid analysis. This kind of reaction is generally known as the Zimmermann reaction. Due to the specific color reaction for 17‐
oxo
‐steroids, the Zimmermann reaction has been routinely used for the various clinical testings. Besides the interference from carbonyl compounds, several limitations of this reaction have been discussed.