Scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) is a moderate resolution imaging spectrometer on board the environmental satellite (ENVISAT) launched in March 2002. SCIAMACHY has eight channels, covering a spectral range from 240 to 2380 nm and observes the Earth's atmosphere in nadir, limb, and occultation geometries. From SCIAMACHY lunar occultation measurements, nighttime vertical profiles of O 3 and NO 2 have been retrieved over the southern hemisphere (60°-90°S) using the optimal estimation method. The first preliminary validation of retrieved O 3 profiles with halogen occultation experiment and comparisons with stratospheric aerosol and gas experiment III (SAGE III), and Michelson interferometer for passive atmospheric sounding (MIPAS) O 3 profiles were carried out. In addition, the retrieved NO 2 profiles were compared to SAGE III and MIPAS results. The results of these preliminary validation and comparisons give confidence that reasonable scientific data products (trace gas profiles) can be derived from SCIAMACHY spectroscopic lunar occultation data. © 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.