Delayed vomiting is a potentially significant adverse effect of chemotherapy used to treat childhood cancer, but little is known about the experience of delayed vomiting in children and adolescents. An exploratory study was conducted to determine the pattern of delayed vomiting in children and adolescents with cancer after highly emetic chemotherapy and to identify possible risk factors. In a sample of 82 children and adolescents who completed 117 cycles of highly emetic chemotherapy, the overall prevalence of delayed vomiting was 32%. The frequency of delayed vomiting was highest on delayed day 2, with 21% of participants experiencing vomiting. By delayed day 7, only 9% of participants still reported vomiting. The severity of vomiting was moderate to severe in 11% to 12% of subjects. Age and gender had no significant effect on delayed vomiting. The emetic potential of the agent, incomplete protection from acute vomiting, and treatment regimens that lasted 6 or more days significantly affected delayed vomiting. In addition, a history of motion sickness, lack of acute control, and 6 or more days of chemotherapy were predictive of delayed vomiting.