Gibberellin A5 (GA5), a native GA of immature seeds of Pharbitis nil, was fed to Pharbitis nil cell suspension cultures as [C-l, 3H] GA5 (3.1 Ci/mmol), and its metabolism over a 48 hr period was investigated. Radioactivity in free GA metabolites was 13.1%, with 79.9% in GA glucosyl conjugate-like metabolites. Only 7.0% of the radioactivity remained as [3H] GA5. Tentative identifications were based on comparison with retention times of authentic free GAs and/or glucosyl conjugates after sequential chromatography on Si gel partition column → gradient-eluted C18 HPLC-radiocounting (RC) → isocratic-eluted C18 HPLC-RC, and showed that [3H] GA5 was converted to [3H] GA1 (2%), [3H] GA3 (4%), [3H] GA6 (2%), [3H] GA22 (1%) and their glucosyl conjugates, and also to [3H] GA8 glucoside, and [3H] GA5 glucosyl conjugates. The major conjugate-like substances were [3H] GA1 and [3H] GA3 glucosyl esters, at 15% and 34%, respectively, of the total extractable radioactivity.