A novel method has been developed for the isolation of microvascular endothelium from first trimester decidua. Enzymatic dispersion and Percoll gradient centrifugation, followed by positive selection using Ulex europaeus coated immunomagnetic beads, yields pure isolates of endothelium. Typical 'cobblestone' monolayers form within 3-5 days; cells express the classical endothelial markers CD31 and Von Willebrand factor and the inducible cell adhesion molecules endothelial-leukocyte adhesion molecule and vascular cell adhesion molecule. Cell growth is dependent on both high concentrations of magnesium ions and human serum. Of the endothelial growth factors examined, only vascular endothelial growth factor stimulated growth, suggesting an important role for this factor in uterine angiogenesis.