Abstract: Electrophoreses on vertical polyacrylamide plate were adopted to analyse 13 clones of Aigioros poplars. Marked differences have been found in peroxide isozyme patterns in Populus nigra, P. deltoides and their hybrids Populus x Euramericana. Each clone of the P. deltoides has 3-4 bands of zymogram. The band with a Rf value of 0.667 is peculiar to P. deltoides. Populus nigra cv. "blane de garonne," a typical clone of P. nigra, has 7 bands of zymogram. Bands with Rf values 0.535 and 0.613 are peculiar to "blane de garonne." Clones of Populus x Euramericand have 4-g bands. They are varied in isozyme patterns. The highly vigorous hybrids of Populus x Euramericana have both the same bands as P. nigra and P. deltoides.The Aigioros clones not only vary in band number but also differ in band Rf value. Some clones are generally alike in their zymograms and similar in Rf values, but vary in enzyme activities.Consequently, we hold that the method of isozyme analysis for identifying Aigioros clones is feasible,- 777 -