Pterocarpin (Fig.1) is a naturally occuring coumarochroman involved with many of its derivatives, which are known for their antifungal activities, in the physiology and the pathology of plants1–7. The UV spectrum already published in the literature(1)has been used for empirical identifications. Its puzzling features have never been explained. The widths of the three observed bands (Fig.2) are obviously too different to assume that these bands are the remains of the vibrational structure of a single electronic transition and they are packed on too a narrow wavelength range to be three different electronic transitions. The bandawhich is the most intense, and the widest one, appears at 310 nm (ϵ-6650). Two sharper ones, respectivelybandc, lie at 286 nm (ϵ 4750) and 280 nm (ϵ =4050). The intensity ofb, when corrected from the overlap withais reduced to ϵ = 2800.