The activities of gibberellins A1–A15, A17–A27 and A8-glucoside are compared, using original and previously published data, in the barley (Hordeum vulgare L.) aleurone α-amylase, Progress No. 9 dwarf pea (Pisum sativum L.), lettuce (Lactuca sativa L.), 'Tan-ginbozu' dwarf rice (Oryza sativa L.), cucumber (Cucumis sativus L.), and the d-1, d-2, d-3, and d-5 maize (Zea mays L.) mutant bioassays. Gibberellins A3 and A7 show high activity in most bioassays. Gibberellins A9, A10, A23, and A24 are species specific in their activity. Gibberellins A8, A11, A12, A13, A14, A17, A25, A27, and A8-glucoside exhibit low activity. Gibberellin A26 is inactive up to 100 μg in all assays. The cucumber hypocotyl and barley aleurone bioassays respond only to a narrow spectrum of gibberellins while the rice bioassay is sensitive to all the gibberellins except A21, A25, and A26.Activity in the cucumber assay is restricted to gibberellins with a 13-deoxylactonic structure. With the exception of gibberellins A8, A26, and A27, only gibberellins having either an oxygenated C-3 position or a C-2,3 double bond, and a 19,10-lactone function, show more than low activity in the barley aleurone assay. Hydroxylation at the C-2 position may account for the reduced activity of gibberellins A8, A26, and A27. Possible reasons for a lack of correlation between gibberellin structure and biological activity in other bioassays are discussed.