At present, three 2-alkyl-1,3-indandiones (PMP, pival, and diphacinon) are widely used as rodenticides. Because analytical procedures now in use are empirical and do not furnish adequate or positive means for distinguishing among these closely related compounds, studies were undertaken to develop a sensitive and specific method for the determination of PMP. The relation between KCN and the 2,4-dinitrophenylhydrazone of PMP was investigated and shown to be sensitive and specific. A deeply colored solution is produced with an absorption maximum at 540 mu. This solution obeys Beer?s law over a wide range. The molar absorptivity for the developed color was calculated to be 3.0 X 104. This reaction can be used also as a spot test to detect as little as 1 ug. of PMP.