Abstract The aims of this work were to analyze the effect of (1) acute doses of gamma rays (1.0–10.0 Gy) on dormant and post-dormant garlic seed cloves, and (2) exogenous applications of growth regulators in reversing the effect produced by irradiation. The results indicated that a 10.0-Gy dose applied in post-dormancy significantly decreased sprouting; sprouts were modified in size (length), color and peroxidase activity. No changes were observed for the dormancy period treatments. The storage leaf showed no modifications. Application of some growth regulators was effective in modifying the effectiveness of the gammarays exposure. Indole acetic acid was the most effective, followed by gibberellic acid; benzyl-adenine gave no evidence of reversal of sprout growth inhibition in in vitro conditions.