With continuing improvements in the successful treatment of pediatric malignancies, long term survivors of pediatric cancers and their providers are faced with new oncologic issues regarding long-term morbidities. As pediatric cancer survivors have matured into adulthood, the development of secondary malignancies has become a significant issue for these patients. Whether a consequence of treatment for the patient's original cancer, such as chemotherapy, ionizing radiation, or hematopoietic stem cell transplantation, secondary malignancies now present patients and providers with new challenges regarding treatment, surveillance and counseling. We review the major risk factors for secondary malignancies in pediatric cancer survivors, with particular emphasis on important molecular and cytogenetic risk factors, both inherited and acquired. We conclude with a discussion of recommendations for surveillance and counseling of these patients.Overall survival for pediatric cancer has steadily increased over the past 40 years, with 5 year relative survival estimates for all pediatric cancers improving from 58% in the mid1970s to greater than 80% in the early 2000s. 1 As therapeutic modalities have been improved and refined over the years, greater proportions of children are surviving their cancer and reaching adulthood. Accompanying this increase in survivorship amongst pediatric cancer patients are long-term complications of therapy, the most worrisome of which is the development of secondary malignant neoplasms (SMN). SMN are defined as histologically distinct malignant neoplasms developing at least two months after completion of treatment for the primary malignancy. 2 However, as several large epidemiological studies in the United States and Europe have shown, the time frame for an occurrence of a SMN are often years to decades after primary treatment has been completed.The Childhood Cancer Survivor Study (CCSS) reported the 30-year cumulative incidence of SMN in 14,359 5-year survivors of childhood cancer to be 20.5%, representing a six-fold increased relative risk (RR) as compared to the general population. 3 According to our estimates from data provided in the Surveillance, Epidemiology, and End Results (SEER) database of the National Cancer Institute, there have been over 1,800 cases of SMN diagnosed in childhood cancer survivors from 1973 to 2010. 4 Figure 1 shows the incidence of SMN by age at diagnosis of the SMN in pediatric cancer survivors. While a majority of SMN developed within 10 years, SMN occurred in childhood cancer survivors up to 30 years after their original cancer diagnosis (Fig. 2).In addition to the rising incidence of SMN in pediatric cancer survivors, SMN remain a significant source of morbidity for these patients. Indeed, it has been reported in long term follow-up of pediatric cancer survivors that death rates due to SMN exceeds that of all other causes, including primary disease recurrence at 25 years from first cancer diagnosis. 5 As survivors of pediatric cancers live longer, it will be imp...