BACKGROUND: While a number of reviews have explored the attitude of health professionals toward euthanasia, none of them documented their motivations to practice euthanasia. The objective of the present systematic review was to identify physicians' and nurses' motives for having the intention or for performing an act of voluntary euthanasia and compare findings from countries where the practice is legalized to those where it is not. METHODS: The following databases were investigated: MEDLINE/PubMed (1950+), PsycINFO (1806+), CINAHL (1982+), EMBASE (1974+) and FRANCIS (1984+). Proquest Dissertations and Theses (1861+) was also investigated for gray literature. Additional studies were included by checking the references of the articles included in the systematic review as well as by looking at our personal collection of articles on euthanasia. RESULTS: This paper reviews a total of 27 empirical quantitative studies out of the 1 703 articles identified at the beginning. Five studies were in countries where euthanasia is legal and 22 in countries where it is not. Seventeen studies were targeting physicians, 9 targeted nurses and 1 both health professionals. Six studies identified the motivations underlying the intention to practice euthanasia, 16 the behavior itself and 5 both intention and behavior. The category of variables most consistently associated with euthanasia is psychological variables. All categories collapsed, the four variables most frequently associated with euthanasia are past behavior, medical specialty, whether the patient is depressed and the patient's life expectancy. CONCLUSIONS: The present review suggests that physicians and nurses are motivated to practice voluntary euthanasia especially when they are familiar with the act of euthanasia, when the patient does not have depressive symptoms and has a short life expectancy and their motivation varies according to their medical specialty. Additional studies among nurses and in countries where euthanasia is legal are needed.