MOLECULES IN AGB STARS OBSERVED WITH ISO

I present in this review the recent results obtained with ISO concerni ng gas phase molecules in evolved stars. The near, medium and far-infr ared spectrum of C-rich and O-rich stars can provide a very important information on the molecular content of these objects. Detailed models for the envelopes of AGE stars are also presented. I also report the detection of triatomic carbon in the far-infrared and I analyze the co ntribution of the re-vibrational lines of the low energy bending modes of polyatomic molecules in the far-infrared spectrum of C-rich evolve d stars.