The program MePASto was developed to facilitate the data reduction and data analysis of Coincidence Doppler Broadening (CDB) spectra. The spectrum is a function of two energies (sampled by detector 0 and detector 1) and can be displayed as a two-dimensional plot. The main problem in data reduction is to find the axis, which represents the coincident events, and to make the data along this axis available for further analysis. MePASto was written at Joanneum University of Applied Sciences, Department of Automotive Engineering, as a student research project by four students in their third semester (Alexander Harrich, Sebastian Jagsch, Stefan Riedler and Walter Rosinger). The program is available free of charge and can be downloaded from http://fahrzeugtechnik.fh-joanneum.at/links/MePASto as a zip-file (mepasto.zip) that includes the program with the setup routine and a 2D spectrum (spectrum.txt) in ASCII format, which can be used for program testing. The spectrum consists of 1025x1025 data points with an energy resolution of 0.073 keV per “pixel”. The program is written in ANSI C with a Visual Basic GUI and can be operated on MS Windows operating systems. It includes a manual, which is available by pressing the “help” button. Additionally you can find a description in http://www.ajur.uni.edu: A.Harrich, S. Jagsch, S. Riedler and W. Rosinger, Computerized Data Reduction and Analysis in Positron Annihilation Coincidence Doppler Broadening Spectroscopy, American Journal of Undergraduate Research, Vol. 2, No. 3 (2003) p. 13. Although the program was tested carefully we cannot guarantee that the program is free of errors or that it will meet your requirements. Unfortunately the program cannot be supported, nevertheless feel free to contact us if you have any comments or if you need further information (guenter.bischof@fh-joanneum.at). Graz, 2004-01-30