Parthenogenetic activation with various combinations of the calciumionophore A23187 and protein synthesis or phosphorylation inhibitors wasinvestigated as a means of producing human parthenogenones with one haploidpronucleus. Unfertilised human aged oocytes exposed to 5 μM A23187 for 5 minwere treated with 10 μg/ml puromycin (puromycin group, 46 oocytes) or2 mM 6-dimethylaminopurine (DMAP group, 42 oocytes) for 5 h. Oocytes treatedonly with A23187 served as a control (control group, 40 oocytes). Afterwashing the oocytes, they were incubated for up to 37 h. Evidence ofactivation (pronuclear formation) and cleavage was observed 18 h and 42 hafter A23187 treatment, respectively. Activation rates in the puromycin andDMAP groups were significantly higher than in the control group (91% (42/46)and 77% (34/44) vs 20% (8/40), p < 0.05, respectively). In thepuromycin group, 81% (34/42) of the activated oocytes showed one pronucleuswith the second polar body (2ndPB), whereas none (0/34) of the activatedoocytes in the DMAP group extruded the 2ndPB. The cleavage rate in thepuromycin group was significantly lower than in the DMAP group (38% vs 68%,p < 0.05). The activated oocytes which had one pronucleus withthe 2ndPB in the puromycin group showed a haploid set of chromosomes(10/13). In conclusion, the combination of A23187 and puromycin is effectivefor producing human parthenogenones with one haploid pronucleus.