It is shown that the most convenient method of preparing prunetin is by the partial demethylation of genistein trimethyl ether with hydrobromic or hydriodic acid under controlled conditions. The 5-methyl ether of genistein (isoprunetin) has now been synthesised by the methylation of 7:4′-O-dibenzyl genistein and subsequent debenzylation. Its properties are very different from those of prunetin and it yields a diethyl ether which could be independently prepared from genistein. The present work conclusively proves that prunusetin cannot be 5-O-methyl genistein (isoprunetin) and should be the same as prunetin.