This chapter presents the case of a 72-year-old man with a 10-year history of Parkinson's disease. He experienced visual hallucinations with preserved insight 2 years previously, subsiding on withdrawal of selegiline. Physical examination revealed a fairly symmetric and moderately severe parkinsonian syndrome, with akinetic-rigid features dominant and little in the way of rest tremor. The initial diagnostic impression was of a dementia syndrome relating to his Parkinson's disease, although the doctor was initially uncomfortable with what he regarded as a normal mini-mental state examination (MMSE) score of 27 out of 30. After 3 and 6 months, repeat MMSE scores were 23 and 25, respectively. Despite some initial diagnostic uncertainty, the patient was commenced on a cholinesterase inhibitor with considerable improvement in his psychotic features and lessening of his periods of confusion. Rationalization of anti-parkinsonian and other medications is an important first step in the management of PD-D.