When barley aleurone layers were incubated with (3)H-Gibberellin A1 ((3)H-GA1), the hormone was converted to (3)H-GA-X (not identified), (3)H-GA8 and two other compounds tentatively identified as (3)H-GA1-glucoside, and (3)H-GA8-glucoside. Uptake and metabolism of the (3)H-GA1 were markedly enhanced by simultaneous treatment with abscisic acid (ABA). Uptake of (3)H-GA1 from the medium containing ABA was linear over a 24-h period, whereas in the absence of ABA, uptake of (3)H-GA1 leveled off after 5 h. After 24 h, aleurones treated with (3)H-GA1 and (3)H-GA1 plus ABA, had taken up 9 and 24%, respectively, of the original (3)H-GA1 provided. Metabolism of (3)H-GA1 proceeded at a linear rate in the presence of ABA. The amount of (3)H-GA1-metabolites which had accumulated by the end of a 24-h incubation appeared to be linearly correlated to the logarithm of the ABA concentration. Gibberellins A8 and-A8-glucoside did not reverse GA1-enhanced synthesis of α-amylase.