Samples of tropospheric air were obtained over the Eastern United States during January of 1978. These samples were analyzed by means of gas chromatography using flame ionization detection to produce vertical profiles of carbon monoxide and methane from the surface to 8 km. The carbon monoxide mixing ratios at 35 ¿N and 45 ¿N agree with previously published values; however, the mixing ratio at 25 ¿N was significantly lower than most previously published values. The methane mixing ratio was found to be beakly dependent on latitude and to have an average value of 1.64 ppm.