Samples of high-intensity crown fire smoke were collected using a helicopter during the International Crown Fire Modeling Experiment near Fort Providence, Northwest Territories, Canada. The samples were analyzed for carbon dioxide (CO2), carbon monoxide (CO), hydrogen (H2), methane (CH4), and total nonmethane hydrocarbons (TNMHC). CO2-normalized mean emission ratios (ERs) and emission factors (g product/kg fuel burned) were determined for CO2, CO, H2, CH4, and TNMHC. Carbon monoxide production was determined to increase during high-intensity crowning. Unlike CO, a corresponding increase in the production of H2, CH4, and TNMHC during crowning was not detected. This represents the first clear indication that we know of where relative increases in CO production from vegetation fires are not positively correlated with corresponding increases in CH4, H2, and TNMHC production. These results may be important to the atmospheric carbon budget, and to the potential use of CO as a normalizing parameter for boreal forest fire emissions. ¿ 1998 American Geophysical Union