As research advances knowledge of illnesses, nurses need to keep abreast of developments. Although advances in knowledge of the pathology of Parkinson's have been limited, there has been some advance in understanding the involvement of the pre-motor areas of the brain and the final pathways to cellular death. This paper, the first of a three-part series, explores current approaches to diagnosing Parkinson's and advances in knowledge of the pathological changes that take place and the signs and symptoms of the condition. In part two of the series, ten common causes of sudden deterioration in Parkinson's will be explored, along with approaches to management. Part three will discuss medical advances in the management of Parkinson's and how these affect the role of the nurse.