Rendering and animating in real-time a multitude of articulated characters presents a real challenge and few hardware systems are up to the task. Up to now little research has been conducted to tackle the issue of realtime rendering of numerous virtual humans. However, due to the growing interest in collaborative virtual environments the demand for numerous realistic avatars is becoming stronger. This paper presents a hardware-independent technique that improves the display rate of animated characters by acting on the sole geometric and rendering information. We first review the acceleration techniques traditionally in use in computer graphics and highlight their suitability to articulated characters. Then we show how impostors can be used to render virtual humans. Finally we introduce a concrete case study that demonstrates the effectiveness of our approach.