Inheritance of four isozymes, GOT, ACP, MDH and ADH, in Populus alba × P. glandulosa was investigated with starch gel electrophoresis. All four isozymes showed bands. For GOT, six or seven loci were postulated and observed segregation of hybrids at five variable loci was in agreement with expected segregation. Two loci were postulated in ACP; one locus showed no variation but the other locus showed variation. As one additional band was found in P. alba × P. alba (italy), hybrids from P. alba × P. alba × P. glandulosa showed more variation than hybrids from P. alba × P. glandulosa. One monomorphic locus and two variable loci were postulated in MDH. For ADH, both parents were turned out as homozygotes but for different alleles and thus all progenies were heterozygotes. ADH in hybrids seems to be a dieter enzyme as it showed on additional band between two parental bands. There were no variation in band betweens of four enzymes among the clones of P alba and P. glandulosa, respectively.