This research aims at developing a design methodology for sliding mode observers for a class of nonlinear systems. The dual problem, that of sliding mode control presents some very interesting features in that in principle it possesses ideal robustness properties in the face of parametric uncertainty and disturbances. In practice, however, control chattering has severely limited the method's applicability. Observer design deals with the problem of reconstructing the state vector from measurements of the system output. For nonlinear systems, observers are currently designed using linearized techniques, particularly extended Kalman filtering. It would be highly desirable to design observers that directly account for the full nonlinear dynamics of the plant, as do sliding mode controllers. This award will allow the exploration of the ideas described above. In developing the theory and considering a simple practical example it should be possible to determine if the appplication of sliding mode observers is truly practical, or contains hidden difficulties.