Simultaneous in situ measurements of stratospheric CH4, 13CH4, N2O, OC18O, pressure, and temperature have been made from Palestine, Texas (32 ¿N) in September 1988 with the JPL Balloon-borne Laser In Situ Sensor (BLISS). Measurements of CH4 and N2O in the altitude range 30-35 km agree well with other measurements, except for an anomalously high value for the N2O at 31 km. Measurements of CH4 support earlier observations of a fold in the vertical profile. A ratio for stratospheric 13CH4/CH4 of 0.0105¿0.0010 implies an enrichment of Δ13C=-45¿92 parts per thousand over the PDB value, in agreement with previous measurements in the troposphere. A large mixing ratio of 1.9¿0.2 ppmv for OC18O is measured, corresponding to an enrichment of Δ18O=280¿50 parts per thousand for the 18O isotopic species over the SMOW value. ¿American Geophysical Union 1992