4-(p-nitrobenzyl)pyridine (NBP) is often used for detection of trichothecenes developed on a thin-layer chromatography (TLC) plate, because this chromogenic reagent enables specific detection of the 12,13-epoxide group of trichothecenes. After the heat reaction with NBP and cooling at room temperature for several minutes, trichothecenes on the TLC plate are visualized as blue spots by alkalization with tetraethylenepentamine (TEPA). When the TLC plate was left overnight and then sprayed with TEPA, most trichothecenes yielded similar blue colors. However, dark yellowish green spots were given for 8-keto-15-hydroxytrichothecenes. This modified detection method can be used as an easy alternative of other instrumental analyses to distinguish between 8-keto-15-hydroxytrichothecenes and other trichothecenes that give similar R_f values on a TLC plate.