Simultaneous in situ measurements of , 2>, 3>, jNO2, 4>, 2O>, 2>, pressure, and temperature in the 40 to 26-km region of the stratosphere were made from Palestine, Texas (32¿ N), on October 16, 1986, using the Jet Propulsion Laboratory (JPL) Balloon-born Laser In Situ Sensor (BLISS) instrument, carrying a University of Denver jNO2 instrument piggyback. Using tunable diode laser absorption spectroscopy over a long path length, measurements were made as follows during a 21-hour flight: daytime , 2>, 2>, and jNO2 near 40 km; , 2>, and jNO2 through the sunset transition near 40 km; postsunset measurements of the rate of decay of 2> into the night over the 35 to 29-km range; nighttime measurements of 2>, 3>, 4>, 2O>, and 2> at 27 km; and after sunrise. The NO, NO2, O3, CH4, H2O, and CO2 concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO2 amounts. Measured O3 concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10% and agree more closely with solar backscattered ultraviolet data at this altitude. The observed change in 2> during the night over a 5-km altitude range implies either lower 2> postsunset profiles, or significantly faster 2> decay than current model predictions using N2O5 chemistry. Measurements of , 2>, 2O>, and 2> from an October 1985 flight are included for comparison. ¿ American Geophysical Union 1987