To define further the place of dexamethasone in antiemetic combinations, lorazepam, prochlorperazine and placebo (LP) were compared with lorazepam, prochlorperazine and dexamethasone (DLP) in a randomised, double-blind, crossover study. Both patient and observer assessments were documented in 84 patients receiving both cisplatin and non-cisplatin chemotherapy. The addition of dexamethasone significantly reduced the severity of nausea (P = 0.002) and vomiting (P less than 0.0001), duration of nausea (P = 0.01) and vomiting (P = 0.002) and the number of vomiting episodes (P = 0.003). DLP was the superior regimen in subsets of patients receiving cisplatin and the non-cisplatin chemotherapy. The improvements produced by the dexamethasone regimen were large and of major benefit to our patients. Patients documented significantly improved tolerance to chemotherapy with DLP courses (P = 0.0006). Overall, significantly more patients preferred DLP (P less than 0.0001). Patient assessments produced results similar to observer assessments but gave a broader understanding of their experience. The addition of dexamethasone to prochlorperazine and lorazepam significantly improved our patients' experience while receiving chemotherapy.