In order to potentiate the efficacy of antiemetic drugs such as metoclopramide (MCP) and the new drug GR 38032F, adjuvant antiemetic drugs such as benzodiazepines are used in cancer patients receiving chemotherapy. The purpose of our prospective study was to investigate the efficacy of alprazolam (APZ), a newer diazepam, as an adjuvant antiemetic drug, when combined with MCP, in carboplatin (JM8)-based chemotherapy. Thus, 42 patients entered this study. First they received only MCP 1 mg/kg in 15 min infusion (arm A). In the next cycle they received the combination of MCP in the same dose and a tablet of APZ 0.25 mg, 30 min before JM8 infusion and then 3.5, 5.5 and 11.5 h after (arm B). JM8 was administered alone (400 mg/m2) or in combination (300 mg/m2) with vinblastine (6 mg/m2), etoposide (100 mg/m2) or 5-fluorouracil (1,000 mg/m2). In arm A, according to the WHO classification, nausea was intense (p less than 0.003) and the duration of nausea longer (p less than 0.002). In arm B more patients did not present vomiting (p less than 0.018). Secondary effects such as appetite (p less than 0.04), diarrhea (p less than 0.064), diaphoresis (p less than 0.085) and headache (p less than 0.024) were worst in arm A. We conclude that APZ increases the antiemetic effect of MCP on JM8. APZ is a useful adjuvant antiemetic drug, especially against the development of anticipatory anxiety, nausea and vomiting that many cancer patients presented during chemotherapy.