We examined the influence of cognitive factors and conditioning variables on anticipatory nausea and vomiting symptoms (ANV) in 32 pediatric cancer patients with postchemotherapy nausea and vomiting (PNV) who received ondansetron. The patients were compared with 18 patients without ANV (NANV). Age, gender, history of motion sickness, aggressiveness of the chemotherapy, PNV severity, number of chemotherapy treatments, number, type, and efficacy of self-reported coping strategies, and expectations of severity of postchemotherapy symptoms failed to differentiate the ANV and NANV groups. The amount of subjective distress associated with nausea and vomiting was significantly greater in the ANV group. Among patients in whom ANV developed, level of distress and expectations of severity of postchemotherapy symptoms were positively correlated with the severity of ANV and PNV symptoms. Therefore, greater distress might increase the likelihood of ANV conditioning. Once ANV is conditioned, cognitive factors might influence the severity of symptoms.