Parkinson disease is one of the most common neurodegenerative diseases in the United States, and the number of late stage patients is rising. In advance-stage disease, fluctuations in motor function, variability in response to dopaminergic therapy, and dyskinesias related to increasing doses of dopamine agonists and levodopa, present a variety of challenges to a managing physician. Traditional methods of treatment have concentrated on therapies to anticipate or prevent states of poor motor function. With the approval of apomorphine as a rapid-acting, subcutaneous injectable anti-Parkinson disease therapy, these off periods may now be treated with apomorphine as a "rescue" medication when they occur. This article reviews the pharmacology of apomorphine, the clinical data that support its use and suggest dosing and methods for initiating therapy in this challenging population of patients with Parkinson disease.