The common monomeric units in the polymeric procyanidins are catechin and epicatechin, which have a hydroxyl group at C(5). This hydroxyl group is absent in the profisetinidins. The fluorescence properties have been characterized for the profisetinidin monomer and dimers, and compared with previous results for the procyanidins. There is a measurable heterogeneity in the fluorescence of fisetinidol, in contrast to the simpler fluorescence of the procyanidin monomers. This heterogeneity is attributed to differences in the photophysical properties of the aromatic A- and B-rings in fisetinidol. These differences are larger in fistinidol than in catechin or epicatechin. The heterogeneity prevents determination by fluorescence of the conformations at the interflavan bond in the profisetinidins by the data analysis employed successfully with the procyanidins.