The purpose of this study was to determine if cancer chemotherapy invariably produces nausea and vomiting, if the extent of emesis is influenced by the number of drugs in a regimen, and if children's patterns of symptoms remain stable during repeated courses of the same agents. Forty-nine children with cancer (ages 5–21) prospectively rated (1–10 scale) their nausea and vomiting within 3–5 days after the administration of each course of chemotherapy. Chemotherapy courses which included antiemetics were eliminated from the analysis. No agents were found which never or always produced nausea and vomiting. No systematic increases or decreases in vomiting occurred as agents were added or subtracted from chemotherapy regimens and there was no association between the number of agents in a regimen and the extent of nausea and vomiting. Most patients' symptoms fluctuated widely. Only 4/49 patients (8%) had minimal symptoms (ratings of 1s and 2s) during chemotherapy and there were no patients who always had nausea and vomiting (ratings ≥ 3s) with every course. The data suggest that nondrug variables influence chemotherapy-associated nausea and vomiting in children.