IRC+10216 is the nearest and brightest C-rich star. It has a rich chemistry characterized by a variety of processes (thermoequilibrium reactions, radical- radical reactions, ion-molecule reactions and possibly grain surface reactions) and a large variety of molecular species. It is the only C-rich envelope where metal-bearing molecules have been found (NaCl, AlF, AlCl, KCl, MgNC, NaCN) and where the long carbon chain radicals have been detected (C5H, C6H). We propose to perform a full spectral survey of this object between 2.38 and 196.7 um using the SWS and LWS instruments. The SWS full resolution grating sweep between 2.38 and 45 um will allow to search for the presence of nearly all likely molecular species by covering their stretching and/or bending vibrational bands. It will also allow to determine their abundances. Many new molecules will probably be detected, and our knowledge of the envelope molecular composition greatly improved. The spectral resolution provided by the SWS full resolution grating observations, R 1500-2000, will permit to resolve the rotational structure of the molecular bands arising from molecules with rotational constants larger than 0.15 cm-1 -- i.e. from practically all diatomic and triatomic species and from some four-atomic molecular species. In order to derive the physical conditions of the gas, we would also like to observe some ro-vibrational lines of known molecular species with the SWS FP instrument. Finally, we would like to perform a fast LWS FP scan of IRC+10216 between 43 and 196.7 um. The signal to noise ratio will be large enough to detect strong absorption or emission lines of heavy molecules or fine structure atomic lines. Key molecules like C3, C4, C5, C6, C4H, C5H, C6H, C4H2, C6H2, ..., have their low lying bending levels in the LWS frequency coverage. The spectral scan will allow to identify these species, precise their spectral constants and study their role in the growth of carbon chains molecules.