The instrument Lumi-Imager was developed for the detection and accurate quantification of chemiluminescent signals on blots and in microtiter plates. It contains a cooled CCD camera, a specially developed lens system and software. In addition to luminescence, Lumi-Imager F1 can also detect and quantify UV-excited fluorescent signals in gels. Here we describe the components and features of this instrument as well as some of its applications.