This article describes a spectrometer used for recording rotationally-resolved spectra of small molecules. The spectrometer consists of a high resolution scanning monochrom-ator and photon counting detector interfaced to a dedicated minicomputer. The interface is very versatile, providing operation in several modes with minimum demands on the computer. This allows the computer to run in a foreground-background mode in which data previously acquired can be analyzed or new software developed while simultaneously acquiring new data with almost complete invisibility.