The detection of interstellar molecules relies on the precise knowledge of spectral line positions from laboratory measurements. Technical developments of recent years have led to an extension of the accessible spectral range towards shorter wavelengths. New telescopes like SOFIA, the HIFI instrument aboard the Herschel satellite, and ALMA will be used for astrophysical observations in the terahertz region. The Cologne group has developed precise spectrometers to study molecules of astrophysical importance under laboratory conditions and to obtain characteristic spectra for their possible detection in space. We present recent results on light hydrides, carbon-chain molecules and more complex species.