The nursing literature of the last 20 years recommends the ventrogluteal site how the best site for intramuscular injections Beecroft, Redick, 1990, but, the few studies done with the aim to discover which is the most frequently used site report that the dorsogluteal site is the one preferred from nurses Farley, Joyce, Long et al., 1996. The propose of this descriptive study is to understand which are the criteria used by nurses when they have to decide which site choose for administering an intramuscular injection. 167 Italian nurses, from the province of Reggio Emilia, that answered at an anonymous questionnaire, compose the sample of this study. The study's outcomes demonstrate that the most frequently site used from the nurses is the dorsogluteal. The most frequently principles that support this choice are the easier access, the large muscle's bulk, the lower sensibility at the pain and the request of the patient. These reasons suggest that the nurses are guided, in choose the site for administering an intramuscular injection, much more by the customs than the evidence.