The purpose of this study was to determine the prevalence and correlates of anticipatory nausea and vomiting in a sample of pediatric patients with cancer who were receiving outpatient chemotherapy. Forty male and female patients representing a broad range of diagnoses were interviewed with their parents concerning nausea and vomiting before and after chemotherapy. Anticipatory nausea was reported by 28.8% of the sample; anticipatory vomiting was present in 20% of the sample. An additional 9% had experienced anticipatory nausea and vomiting in the past but not currently. Anticipatory nausea and vomiting was positively correlated with the emetic potential of chemotherapeutic regimens and the severity of nausea and vomiting after chemotherapy; anticipatory nausea and vomiting most often developed within the first 4 months of treatment. Onset of anticipatory nausea and vomiting usually occurred two to four hours before treatment and was most severe at the actual time of drug administration. Considerable interpatient variability was observed, with treatment-related factors accounting for only 22% of the variance in the occurrence of anticipatory nausea and vomiting. These findings are considered within a behavioral framework for understanding conditioned aversions in pediatric patients with cancer. Implications for patient education, future research on the prediction of children at risk, and intervention are discussed.