O-2 lancing is one of the industrial techniques for implementing oxygen-enhanced combustion (OEC), and can potentially result in stable combustion with reduced NO, emissions. The key technical challenge facing lancing (and OEC in general) is the significant cost of O-2 enrichment. The present work reports early results from a study of CH4 OEC, in which the O-2 enrichment of air is implemented in situ using dense, high-temperature mixed-conducting solid-oxide membranes. We report on the preparation and characterization of these membranes, and on the fundamental combustion studies of the relevant reactive mixtures, including the effect Of O-2 lancing on the NO, and CO emissions of fuel-lean and fuel-rich CH4/air premixed flames. (C) 2003 Elsevier Science Ltd. All rights reserved.