The objective of this experiment was to evaluate the male sterilizing activity induced by the chemical hybridizing agent (CHA) clofencet, on four wheat varieties: two Triticum aestivum cultivars, 'Pia' and 'Claudia', and two Triticum turgidum var. durum cultivars, 'Capri' and 'Ambra'. The CHA was sprayed at two stages of the Feekes scale, 7.5 and 8.5, using four rates of active ingredients (0, 3.5, 5.0 and 6.5 kgּha -1 ) in a split block design with fi ve replicates. The effi ciency of the treatments was determined by measuring developed seeds and calculating male sterility (MS). Results showed that MS increased with increasing dosage and was more pronounced at the latest stage of development. The MS average for the highest dosage was 47.3% in the fi rst stage of application and reached 84% at the second stage of application. Cultivars responded differently to the CHA, but no differences clearly attributable to species could be detected. T. aestivum cultivar 'Pia' reached 96% MS, a value that justifi es the use of clofencet as a CHA for hybrid wheat production. The insuffi cient levels of MS detected in the other cultivars were due to causes not determined in this study.