This paper describes a monitoring system that imple- ments real-time face detection. The structure of the system is based on multiple cues that discard non face areas as soon as possible: we combine motion, skin, and face de- tection. The latter is the core of our system and consists of a hierarchy of small SVM classifiers built on the output of a feature selection procedure. Following face detection, a Kalman tracking on the face region allows us to optimize re- sults over time. We present an experimental analysis of the face detection module and results obtained with the whole system on the specific task of counting people entering the scene.