Parthenogenetic embryonic stem cells (ESCs) have been proposed as an alternative source of ESCs. These have been isolated in mice from homozygous and heterozygous parthenotes and pluripotency demonstrated by the production of chimaeric mice. The aim of the present study was to examine whether ESCs could be isolated from porcine heterozygous parthenotes. In vitro matured oocytes derived from abattoir ovaries were used.¹²  Heterozygous parthenotes were produced by arresting oocytes at metaphase I stage using cytochalasin B or D after 20 hours of maturation. Treatments were continued for 22 hours and oocytes were then activated electrically. Treatment with cytochalasin D increased cleavage rate (82.8% vs 69.2%), blastocyst formation rate (49.6% vs 37.1%), primary outgrowth formation (16.4% vs 0.8%), and the number of primary cell lines (5 vs 0) compared with cytochalasin B. Interestingly, the morphology of heterozygous primary cell lines resembled that of previously isolated ESCs more than those from homozygous parthenotes isolated previously (unpublished results). While the production of ESC from homozygous porcine parthenotes using cytochalasin B has been reported previously, this is the first time to our knowledge when putative ESC lines has been isolated from heterozygous parthenotes using cytochalasin D. The pluripotency of these lines is currently being determined.