This paper is a preliminary report on an investigation into the peroxidase iso-enzyme pattern variations in poplar parents and their controlled-pollination progenies. The aim of the investigation was to find a fast and reliable method for identifying the hybrids and evaluating the genetic variations. The peroxidase isoenzymes in combinations Populus deltoides cv. 69/55×P. simonii and P. deltoides cv. 69/55×P. maximowiczii were found to combine their parents bands. Therefore, it is reasonable to believe that the progenies carry the genetic imformation of the parents and are true hybrids. In these hybrids, the peroxidase bands show a regular variation. The F1 progeny of P. deltoides cv. 69/55×P. simonii (or P. maximowizii) shows a regular-segregation with the expected 1:1 Mendal ratio.