In this paper, the performance of Geiger-mode avalanche photodiode (GAPD) receivers for range detection laser radar sensors is reported. The distribution of the non-linear avalanche detections is developed as a function of laser radar pulse width and energy for a given target and clutter range resolved cross-section with additive background noise. This distribution is then employed to design an efficient signal simulator, which was utilized to model performance and verify theory. Finally, an expression for the pulse energy that optimizes the probability of detection for partially obscured targets is given.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.