AbstractA new reversed phase high‐performance liquid chromatographic method was used to quantify iridoid content in plant extracts. Two varieties ofPenstemon rydbergiifrom different locations in the Western United States were found to contain the iridoid glycosides euphroside, aucubin, geniposidic acid and plantarenaloside together with the phenylpropanoid glycoside verbascoside. While one variety showed a tenfold dominance of plantarenaloside over euphroside, the reverse was true of the other variety. The previously reported new iridoid glycoside pinifolin was shown to be an artefact from plantarenaloside since it could be isolated from a boiled extract, but not from a cold extrac