To cope with rising demands for increased blood supply during pregnancy, the vasculature of the uterus undergoes several adaptive changes, including increased permeability, angiogenesis and vasodilatation. Although it is clear that vascular endothelial growth factor (VEGF) plays a paramount role in achieving these adaptations, little is known about regulation of VEGF expression in endometrium during pregnancy. Thus, we have investigated whether luteinizing hormone (LH) and tumour necrosis factor-alpha (TNFalpha) may affect VEGF secretion by stromal cells during early pregnancy in pigs. Real-time reverse transcription/polymerase chain reaction (RT/PCR) of VEGF120 and VEGF164 gene expression revealed significantly higher levels of VEGF164 mRNA in cultured stromal cells (p < 0.0001). The LH-stimulated secretion of VEGF was detected after 24 and 48 h of treatment when doses 50 and 100 ng/ml were used (p < 0.05 and p < 0.01, respectively). The TNFalpha-induced secretion of VEGF by stromal cells was detected only after 24-h treatment with the highest dose used in the experiment (50 ng/ml; p < 0.05). Although the influence of LH on VEGF secretion was more visible compared with TNFalpha, both factors may be considered as potential modulators of adaptive changes in uterine vasculature occurring during pregnancy in the pig.