An optically accessible flame tube combustor is described which has high temperature, pressure, and air flow capabilities. The windows in the combustor measure 3.8 cm axially by 5.1 cm radially, providing 67% optical access to the square cross section flow chamber. The instrumentation allows one to examine combusting flows and combustor subcomponents, such as fuel infectors and air swirlers. These internal combustor subcomponents have previously been studied only with physical probes, such as temperature and species rakes. Planar laser-induced fluorescence (PLIF) images of OH have been obtained from this lean burning combustor burning Jet-A fuel. These images were obtained using various laser excitation lines of the OH A$IMPX (1,0) band for two fuel injector configurations with pressures ranging form 1013 kPa (10 atm) to 1419 kPa (14 atm), and equivalence ratios from 0.41 to 0.59. Nonuniformities in the combusting flow, attributed to differences in fuel injector configuration, are revealed by these images.