Nausea and vomiting are important complications after craniotomy, for which there are little published epidemiologic data. We retrospectively examined the incidence of postcraniotomy nausea and vomiting to define risk factors. Medical records from 199 adults undergoing elective craniotomy were identified. Data extracted from surgery and the initial 48 hours postoperatively included gender, age, supratentorial versus infratentorial craniotomy, type of anesthesia (general versus monitored anesthesia care), intraoperative fentanyl dose, duration of anesthesia, antiemetic administration intraoperatively and postoperatively, and incidence of postoperative nausea, emesis, and opioid use. Postoperative nausea was recorded in 99 patients (50%) and emesis in 78 patients (39%). Postoperative opioids were administered to 170 patients (85%). Antiemetics were given intraoperatively to 13 patients (7%) and postoperatively to 121 patients (61%). More women (61%) than men (37%) had nausea (P = 0.001); emesis (women = 46%; men = 31%, P = 0.03); and postoperative antiemetic use (women = 69%; men = 51%, P = 0.013). The incidence of postoperative nausea (P = 0.04) and vomiting (P = 0.06) was greater in patients having infratentorial surgery. Emesis was more frequent in younger patients (P = 0.03). Postoperative nausea and vomiting were independent of anesthetic duration, fentanyl dose, or postoperative opioid use and occurred with similar frequency after general anesthesia or monitored anesthesia care. We conclude that postoperative nausea and vomiting occur frequently after craniotomy. Infratentorial surgery, female gender, and younger age are significant risk factors for this complication.