Effects of growth regulator applications on the flowering of 5-years-grafted mature scions of Picea sitchensis (Bong.) Carr. were assessed. Growth regulators were applied to the bud surface in droplets of ethanol during July, August and September in a polythene house or glasshouse. A mixture of gibberellins A4 and A7 applied alone, and in combination with gibberellins A3 and A5, significantly increased numbers by up to seven times for male and by up to eight times for female strobili, gibberellin A, gave relatively the strongest response, and gibberellin A4 was inactive. Phosphon D and abscisic acid each reversed the promotion of flowering by gibberellins, whilst kinetin and N,N-diphenylurea had no effect. The number of female strobili was negatively correlated with vegetative shoot length in the year after treatment. Under field conditions hormones were applied in July and August under flaps of bark on the branches of 10-years-grafted mature scions. Gibberellin applications caused a 5-fold increase in flowering and N6-benzyladenine further increased the response. Naphth-lyl-acetic acid reduced female and increased male flowering. Bark removal near the base of the branch further enhanced hormone-induced strobilus production. The usefulness of these findings for the breeding of Picea sitchensis is discussed.