AbstractA new high performance liquid chromatographic technique has been developed for the rapid analysis of sesquiterpene phytoalexins such as capsidiol, rishitin, lubimin and phytuberol. This method employs a cyanopropyl‐bonded phase column with an isocractic mixture of hexane and isopropanol. When used with a flame ionization detector the lower limits of detection are about 0.1 μg and the response of the detector is linear in the range 0.1–30 μg. With the UV detector at 205 nm, the lower limits of detection are about 0.1 μg for capsidiol and rishitin and 0.5 μg for lubimin, phytuberol and debneyol. The response of the UV detector is linear in the range 0.5–30 μg. Although both detectors proved to be useful, the signal response with the flame ionization detector was proportional to the mass of each of the phytoalexins, while the signal with the UV detector was proportional to the number of carbon‐carbon double bonds in each of t