A cooperation project between the Geological Survey of Namibia (GSN) and the Bundesanstalt fur Geowissenschaften und Rohstoffe (BGR, Federal Institute for Geosciences and Natural Resources, Germany) ran from 1992 to 1996 and covered the refinement, compilation and interpretation of existing open-file airborne geophysical data. As part of this cooperation, the refinement and compilation of regional airborne gamma-ray data was undertaken over two selected areas. From 1968 Namibia was gradually covered by government funded airborne geophysical surveys. Most of these surveys were always in conjunction with magnetic surveys. Typical traverse spacing was 1000 m with a survey height about 100 m above ground. Most of the gamma-ray data were processed immediately after surveying, but map production was of an inconsistant standard, and in some cases a few survey blocks were never processed. The merging of the various survey blocks had never before been tackled, partly as a consequence of the various detector sizes used during the course of time. It was only in the early nineties when back-calibration and reprocessing of airborne gamma-ray data were made feasible. It soon became evident that merging and compiling the Namibian airborne gamma-ray data would be useful to support geological mapping, to contribute to environmental issues and to determine the general background radiation. As the Namibian airborne gamma-ray data vary in quality, it was agreed by the GSN and the BGR not to compile all the existing airborne gamma-ray data, but rather to select an area to test methodology, cost effectiveness and quality of the final compilation products. The area selected covered four 1 : 250000 scale map sheets, namely 2014 (Fransfontein), 2016 (Otjiwarongo), 2114 (Omaruru) and 2116 (Okahandja) in west central Namibia. This area comprised data collected from the earliest 1968 surveys (merely analogue charts) to more modern (tape records) surveys flown in 1980. In this way it was possible to gain practical experience with the Namibian gamma-ray data and to see whether it would be worth compiling greater portions of the data in the future. The aim was the compilation of a 1 : 250000 scale map series consisting of individual map sheets showing the ground level exposure rate, the ground concentrations of potassium (K), thorium (Th) and uranium(U) as well as elemental ratios. This was to be achieved by comparing the airborne measurements with ground measurements using a calibrated portable gamma-ray spectrometer. In fact, back-calibration and compilation of the west central Namibian data were successful and stimulated to process and compile all the open-file airborne radiometric data of southern Namibia that was a priority target area of the cooperation project. This bulletin gives detailed information on the data processing and compilation and provides interpretation summaries for each 1 : 250000 scale map sheet. This is to support the user of the radiometric map series in his understanding of the radiometric patterns and their significance in terms of prospectivity for natural radio-elements, lithology, and soil chemistry.