The present invention provides a method for the determination of NAD(P)H which comprises reacting a chromogen represented by the following general formula (I): ##STR1## wherein Y is hydrogen or hydroxyl; R.sub.1, R.sub.2 and R.sub.3 may be the same or different, and are groups represented by the following general formula (II), (III) or (IV): ##STR2## wherein Z is hydrogen, hydroxyl, amino, substituted amino, alkyl, substituted alkyl, alkenyl, aryl, substituted aryl, acyl, halogen, nitro, sulfo, carboxyl or alkoxy; n is 1, 2, or 3; provided that at least one Z in R.sub.1, R.sub.2 and R.sub.3 is hydroxyl, amino, or substituted amino; and Z.sub.s in Z.sub.n may be the same or different, with NAD(P)H in the presence of (1) peroxidase or thiol oxide reductase and (2) diaphorase or an electron carrier, and determining the pigment thus formed.