A refined technique of gel electrofocusing revealed the esterases in caryopses of Triticum aestivum, T. durum, and Triticum timopheevi. In T. aestivum, 17 isoenzymatic bands were ascertained in the pH 5-8 range: 11 were of higher intensity, 4 were weak and two very weak. Using Chinese Spring nulli-tetrasomic lines it was possible to locate the genetic control of several isoenzymes in the chromosomes of the homoeologous group 3. In chromosome 3A three bands are coded; in 3B four bands are coded; and in 3D two bands out of the eleven of higher intensity. T. durum, as expected, lacks bands coded in T. aestivum by chromosome 3D. T. timopheevi presents a quite distinct isoenzyme pattern, thus confirming its different speciation. Two major bands do not disappear in any of the nulli-tetra lines analyzed: it is supposed that these isoenzymes could be coded by at least two of the chromosomes of the group three involved in esterase control. The presence of several esterase isoenzymes in wheat is both evidence of their additivity with increasing ploidy level and biochemical support for the hypothesis that there is a higher possibility of adaptation of polyploids compared with diploid species.