Within the years 1996-2005 at Plant Breeding and Acclimatization Institute, Research Division Młochów genetic variation of 2x potato was being transferred into 4x level in interploidy crosses 4x-2x. In eight crossing cycles 233 combinations of 4x progenies were obtained. Out of them 57 were used in tetraploid parental breeding lines. They were obtained among 16 diploid donors of new alleles of chosen traits and 23 tetraploid females. Efficiency of seed setting in these crosses ranged from 0.9 to 171.0 seeds per berry. As a result of selection and comparative analysis among the progenies originating from 4x-2x crosses and standard 4x-4x progenies, 2x clones were distinguished as perspective parents for tetraploid breeding. They were as follows: HT/HZ 84-PH 151, DG 88-89, DW 88-4556, DG 93-332 and DG 97-943 for processing; DG 88-89 and DW 88- 4556 for table use; HT/HZ 84-PH 151 for high starch content; DG 91-234 for resistance to Phytophthora infestans and DG 88-9 for resistance to Erwinia carotovora.