GESPECOR is a Monte Carlo based software developed for the computation of e
fficiency, of matrix effects and of coincidence summing effects in gamma-ra
y spectrometry. GESPECOR can be applied to coaxial and well-type HPGe or to
Ge(Li) detectors and to various types of sources, including point, cylindr
ical, and spherical sources or Marinelli beakers. In this paper the structu
re of GESPECOR is presented and the procedures applied are described. The u
ncertainty of the results computed by GESPECOR is carefully analyzed. The a
nalysis shows that GESPECOR is able to provide results with a well defined
uncertainty, in a user friendly WINDOWS environment.