Fifteen cancer patients receiving cisplatin-containing chemotherapy participated in two antiemetic studies. In Study 1 they received standard antiemetics in low doses on demand, and in Study 2 the same patients participated in an open randomized cross-over study between metoclopramide 1 and 2 mg/kg i.v. X 5. Serum metoclopramide was determined by HPLC. Self-reporting of nausea using a visual analogue scale (VAS) was compared with observer rated scores. Tolerability and volume vomited were assessed by nurse observers. The biological half-life of metoclopramide was 9.9 h, the volume of distribution was 9.9 l/kg and the clearance was 0.68 l/h/kg. The pharmacokinetics of high dose metoclopramide was linear in the range 0.15-2 mg/kg X 5, with very little accumulation. Compared to standard antiemetics, both high dose regimens of metoclopramide had a significant effect on nausea, but no effect on the volume vomited. Self reports of nausea were significantly correlated with observer rated values. Tolerance of high dose metoclopramide was good except in 3 patients who left the study because of restlessness and trismus. It is concluded that high dose metoclopramide probably can be administered for several consecutive days without appreciable accumulation of the drug. Self-reporting of nausea by patients on VAS is a simple and feasible method of evaluation. The finding that metoclopramide affects nausea but not vomiting supports the hypothesis that nausea and vomiting should be evaluated separately in assessing antiemetic efficacy.