Presented in this paper is an on-going project to develop a new generation of virtual human models that are highly realistic in terms of appearance, movement, and feedback (evaluation of the human body during task execution). Santos™ is an avatar that exhibits extensive modeling and simulation capabilities. It is an anatomically correct human model with more than 100 degrees of freedom. Santos™ resides in a virtual environment and can conduct human-factors analysis. This analysis entails, among other things, posture prediction, motion prediction, gait analysis, reach envelope analysis, and ergonomics studies. There are essentially three stages to developing virtual humans: (1) basic human modeling (representing how a human functions independently), (2) input functionality (awareness and analysis of the human’s environment), and (3) intelligent reaction to input (memory, reasoning, etc.). This paper addresses the first stage. Specifically, we discuss a new human model in terms of mechanics and appearance. We present an optimization-based approach to kinematic and dynamic motion analysis. This approach allows the avatar to operate with complete autonomy rather than with dependence on stored animations and data, or restrictions associated with inverse kinematics. With dynamic analysis, it is not necessary to solve equations of motion. A novel approach for determining reach envelopes is also presented, and this approach provides a unique tool for ergonomic studies. Methods for evaluating the physiological status of the virtual human as tasks are completed are discussed. Finally, additional on-going research is summarized. The result is an exciting step towards a virtual human that is more extensive and more complete than any other.