Plants belonging to the Coleus and Plectranthus genera of the Labiatae were semi-quantitatively assayed for the presence of forskolin, a potent cardioactive and hypotensive diterpenoid under development. In the TLC and GLC assay methods employed, forskolin could be detected at levels down to ca. 1 × 10-4 % of the dry plant material. Coleus forskohlii Briq. appears to be unique in that it is the only species among those assayed which was found to contain forskolin.