Michelson interferometer for passive atmospheric sounding (MIPAS) is operating on board of the ENVISAT satellite and is acquiring for the first time high spectral resolution middle infrared emission limb sounding spectra of the Earth atmosphere from space. An optimized code was developed for the Level 2 near real time analysis of MIPAS data. The code is designed to provide, in an automated and continuous way, atmospheric vertical profiles of temperature, pressure and concentrations of O-3, H2O, CH4, HNO3, N2O and NO2, in the altitude range from 12 to 68 km. The performances of the code are herewith derived from the analysis of the first measurements acquired with this instrument. The assumptions made for the development of the optimized code are verified with the real data. The diagnostics of the instrument performances provide indications that there is good agreements with the results obtained by the Level 1 analysis. Consistent geophysical data are retrieved which is a first step towards a more complete assessment of retrieval accuracy. The tests have identified the possibility of measurement improvements by way of some secondary operations such as a correction of the frequency scale and the use of cloud filtering. However, no change in the algorithm baseline appears to be necessary. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.