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Organic molecules in comets, meteorites and the interstellar medium are discussed with attention to gas phase and grain surface formation pathways in dense interstellar clouds. The most important spectroscopic evidence in the diffuse interstellar medium is reviewed. Signatures and unsolved problems related to the main organic components thought to be present in the diffuse gas are criticized and circumstellar formation of organics around late-type stars considered. Recent observations with the Infrared Space Observatory and ground-based radiotelescopes have been important in this field.