Tests with gibberellins indicate several uses in grape production. They were found to produce an excellent set in Black Corinth. They also greatly increased berry size of Thompson Seedless when the sprays were applied at the proper time for girdling. Gibberellin can be applied in conjunction with girdling or separately. In some cases gibberellin applied separately produced larger berries than those obtained from girdling only. The largest berries resulted from a combination of girdling and treatment with gibberellin.