Objective: To analyze directional vascular endothelial growth factor (VEGF) secretion in polarized human endometrial epithelial cell cultures. VEGF has distinct distribution patterns in human endometrium. Stromal cells are diffusely positive for VEGF messenger RNA and protein, whereas glandular epithelium shows focal VEGF immunostaining at the apical surface. The epithelial distribution suggests that VEGF is secreted into gland lumina, potentially influencing the nutrition and/or apposition of the developing blastocyst. Design: Controlled in vitro study of protein secretion by polarized endometrial epithelial cells established on polyethylene filters Setting: University hospital. Patient(s): Endometrial biopsies were obtained from healthy, ovulatory women undergoing elective surgery. Intervention(s): Primary endometrial epithelial cells were cultured. Main Outcome Measure(s): VEGF mRNA and protein production were measured in polarized cells. The vectorial secretion of VEGF was determined. Result(s): VEGF production by endometrial epithelial cells was verified by Northern blotting and immunoassays of conditioned media. The mean (±SD) apical secretion of VEGF was 3.9 ± 1.4 ng per 105 cells every 48 hours and the mean (±SD) basal secretion was 0.8 ± 0.2 ng per 105 cells every 48 hours. In contrast, the apical and basal secretion of a soluble cellular isoform of fibronectin were 2.76 ± 0.96 ng per 105 cells every 48 hours and 2.64 ± 1.79 ng per 105 cells every 48 hours, respectively. Conclusion(s): VEGF is secreted preferentially into the lumina of endometrial glands. Apical VEGF may be an endometrial signal for blastocyst development or implantation.