A continuously recirculating xenon optical pumping apparatus was constructed and coupled to a 200 MHz NMR spectrometer. Steady-state Xe-129 polarizations as high as 69% were achieved approximately 5 min after circulation was begun, and this polarization is >3.5 times larger than observed for single pass operation. Using this apparatus, spin polarization induced nuclear Overhauser effect (SPINOE) experiments were performed on porous silicon samples and on (CD3OD)-C-13 adsorbed on TiO2-coated optical fibers to evaluate the capabilities of the system for studying low surface areas samples. The C-13 enhancement achieved was approximately 14. The recirculating optical pumping system provides high xenon polarization at moderate laser powers for a variety of NMR studies. (C) 2004 Elsevier B.V. All rights reserved.