The proposed study will explore the relationship between temperament and child psychological adjustment in a sample of children during their first year after cancer diagnosis (N = 160, ages 2-18). Multilevel growth modeling will evaluate the longitudinal relationship between three dimensions of temperament (effortful control, extraversion/surgency, negative affect) and trajectories of two psychological adjustment variables (externalizing problems, anxiety/depression scores) across twelve time points. While the primary goal of this study is exploratory, we offer the following predictive hypotheses: (a) psychological adjustment will improve over the course of treatment; (b) negative affect will be associated with higher anxiety/depression and lower externalizing problems; (c) effortful control will be associated with lower externalizing problems; (d) extraversion/surgency will be associated with lower anxiety/depression and higher externalizing problems. The proposed study has numerous advantages over comparable studies in this area of research, such as its relatively large sample size, longitudinal structure with a large number of time points, and measurement of temperament across three specific dimensions. Findings from this study may help health care providers anticipate and mitigate negative psychological outcomes in pediatric cancer patients. Additionally, the findings may inspire future research directions involving temperament and other outcome variables, such as health-related quality of life and family adjustment.