The ISO/LWS far infrared spectrum of IRC+10 216.

We present an ISO Long Wavelength Spectrometer (LWS) grating spectrum of the carbon-rich circumstellar envelope -CSE- of IRC+10216 between 43 and 197μm. The spectrum consists of strong dust emission plus a forest of emission lines from CO, HCN, H^13^CN and vibrationally excited HCN (ν_2_=1^1^,2^0,2^ and ν_1,3_=1). All the CO lines between J=14-13 and J=39-38 have been detected while lines of HCN with J_u_ as high as 48 have also been observed. The molecular emission arises from the warm and dense gas located in the innermost zone of the CSE. The CO and HCN emission can be easily explained if the vibrational and rotational temperatures are around 700-1500 K. We also report the tentative detection of the bending mode of the C_3_ molecule around 62cm^-1^ (157.2μm).