Outcrossing rates in potato were measured in an open-pollination field experiment at a location in the Peruvian Andes. Embryo spot, a dominant genetic seed marker, was used to measure outcrossing rate. The source of the dominant marker, the donor, was interplanted among recipient clones lacking the marker (recessive genotype), for which outcrossing was to be measured. Eight out of the 17 clones tested were advanced breeding clones which had wild species cytoplasm. Seven out of eight of these had outcrossing rates above 0.75, showing complete male sterility in one case and partial male sterility in six cases. Among the other clones tested, which were male-fertile, outcrossing estimates ranged from 0.10 to 0.74. Wide variability in outcrossing rate in autotetraploid potato suggests that it should be possible to select for higher outcrossing rate in production of open-pollinated true seed populations of potato for genetic or commercial purposes.