The Sandia steady, laminar, one-dimensional, premixed flame code is used to investigate NO formation in a series of lean-premixed CH4/O-2/N-2 laminar flames at pressures of 1-14.6 atm. Two different chemical kinetic mechanisms are evaluated in this study. The first mechanism, originally proposed by Glarborg et al. and then modified by Drake and Blint (GMK-DB), is an older mechanism that has previously been shown to be superior to other early mechanisms when making quantitative predictions of NO concentration in lean, high-pressure laminar flames. The second mechanism is the newer GRI mechanism version 2.11. The modeling results for both mechanisms are compared to laser-induced fluorescence (LIF) measurements of NO concentration in the postflame region of a series of flat, laminar, lean (0.5 less than or equal to phi less than or equal to 0.8), premixed flames (N-2/O-2 dilution ratio of 2.2) stabilized on a water-cooled McKenna burner. The GRI mechanism, despite uniformly underpredicting NO formation in these flames: is shown to produce better qualitative agreement under these conditions than the GMK-DB mechanism. The study is then extended to a wider range of equivalence ratios (0.6 less than or equal to phi less than or equal to 1.6) at an N-2/O-2 dilution ratio of 3.1. The results demonstrate that the GRI mechanism is not yet suitable for the quantitative prediction of NO concentrations in rich, premixed flames.