Occultation of the star Regulus-&agr; Leo-by the Jovian atmosphere was monitored by the Voyager 2 spacecraft on July 9, 1979. The absorption recorded in the 910--1200 ¿ range was caused primarily by the H2-Lyman and Werner bands. These data provide the first complete measurements of atmospheric density and temperature profiles between 330 and 830 km above the ammonia cloud tops. The molecular hydrogen density at 380 km is found to be 3+4-1¿1013 cm-3, where the atmospheric temperature is 200¿50 K. The thermal gradient above 830 km altitude is found to be approximately 1 K km-1 to reconcile the stellar occultation data with the Voyager 1 solar occultation data for the exosphere. Both experiments were performed in the equatorial region. The observed temperature gradient in the upper atmosphere rules out inertia gravity wave propagation as the primary heating mechanism; the heating must be caused by one or many of a host of other potential sources such as magnetospheric electrons (soft or hard), Joule heating and even solar extreme ultraviolet radiation. The data do not present a strong argument in favor of an earthlike mesopause on Jupiter. The absorption in the 1250--1600 ¿ range yields volume mixing ratios of methane and ethane of 2.5+3-2¿10-5 and 2.5+2.0-1.5¿10-6, respectively, at a height of 325 km above the ammonia cloud tops. An upper limit of 2.5¿10-6 for the mixing ratio of acetylene has been found at the altitude of 300 km. The Voyager infrared data yield mixing ratios of these hydrocarbons deeper in the stratosphere. A study of the density profiles of the hydrocarbons deduced from the stellar occultation data yields a value of the eddy diffusion coefficient at the homopause to be 1.4+0.8-0.7¿106 cm2 s-1 in the equatorial region which is consistent with the value deduced from the hydrogen Lyman alpha and helium 584 ¿ emission data. Detailed aeronomical implications of the results are discussed elsewhere (Atreya et al., 1981).