We analyze visibility from static sensors in a dynamic scene with moving obstacles (people). Such analysis is considered in a probabilistic sense in the context of multiple sensors, so that visibility from even one sensor might be sufficient. Additionally, we analyze worst-case scenarios for high-security areas where targets are non-cooperative. Such visibility analysis provides important performance characterization of multi-camera systems. Furthermore, maximization of visibility in a given region of interest yields the optimum number and placement of cameras in the scene. Our analysis has applications in surveillance - manual or automated - and can be utilized for sensor planning in places like museums, shopping malls, subway stations and parking lots. We present several example scenes - simulated and real - for which interesting camera configurations were obtained using the formal analysis developed in the paper. © Springer-Verlag 2004.