GH receptor (GHR) mRNA is expressed in bovine in vitro produced embryos up to the blastocyst stage and GH improves the quality of bovine embryos by increasing blastocyst cell numbers and reducing the incidence of apoptosis as evaluated by DNA strand-break labelling. Porcine in vitro produced blastocysts have lower cell numbers than in vivo blastocysts and exhibit higher incidences of apoptosis. Therefore we investigated the effects of 100 ng GH/ml NCSU23 medium during in vitro culture of presumptive in vitro fertilized sow zygotes on embryo development and blastocyst quality (defined by diameter, cell number, apoptosis and survival after non-surgical transfer). In vivo produced blastocysts were analysed concurrently as a reference value. GHR was expressed in embryos from the 2-cell to blastocyst stages. GH had no effect on blastocyst development or cell numbers, but increased the mean blastocyst diameter. The incidence of apoptosis, detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL), was decreased by GH, but when non-TUNEL-labelled apoptotic fragmented nuclei were included, no difference was seen. GH appeared to slow down the progression of apoptosis though. In vivo produced blastocysts presented no apoptotic nuclei, and contained higher cell numbers and larger diameters. Pregnancy rates on day 11 were similar for all groups, but survival was poorer for in vitro than in vivo produced blastocysts. In this study GH appeared to be beneficial only from the blastocyst stage, but the presence of GHR from early cleavage stages nevertheless indicates a role for GH throughout porcine embryo development and deserves further investigation.