Derivatives of 2-and 3-benzo [b] furancarboxylic acids were prepared and evaluated for their cytotoxic potential in the National Cancer Institute, Bethesda, USA. Six compounds: 7-acetyl- 6-hydroxy-3-methyl-2-benzofurancarboxylic acid (2), 6-hydroxy-7-(p-methoxycinnamoyl)-3- methyl-2-benzofurancarboxylic acid (4), 5-bromo-7-hydroxy-6-methoxy-2- benzofurancarboxylic acid methyl ester (6a), 6-acetyl-5-(O-ethyl-2′-diethylamino)-2- ...