A phenotypic segregation of kanamycin resistance conferred by nosnptII was investigated in two groups of transgenic cucumber lines one containing the PR-2duidA-nosnptII construct and the other with the thaumatinII-nosnptII construct to the third and fifth generation, respectively. Expression of the nptII gene was more stable and predictable in the progeny of the PR-2d lines than that of thaumatin lines. In T2 and T3 generations representing seven PR-2d primary transformants, 78% of the hemizygous progenies exhibited a segregation ratio consistent with Mendelian inheritance; non-Mendelian ratio occurred in the remaining 22%. Mendelian segregation was observed in 46% of the hemizygous progenies derived from 11 thaumatin primary transformants. The segregation ratio for two and three independent loci appeared in single PR-2d and thaumatin lines, respectively.