The purpose of this study was to estimate the prevalence of U.S. children's overweight risk and obesity at 9 months and 2 years of age, assess weight changes between the two periods, and examine the relationship between weight statuses. Analyses of children's early weight trajectories and related demographic characteristics from the Early Childhood Longitudinal Study–Birth Cohort (ECLS-B) was undertaken. The nine-month- and two-year-old ECLS-B waves were used to generate a nationally representative estimates of obese and at-risk children born in 2001. Logistic and multinomial logistic regression models were used to determine the odds of children's demographic characteristics being related to weight persistence, loss or gain. Approximately one-third of U.S. children were either at-risk or obese at nine months and two years. Some groups were at greater risk. Obesity risk was not uniform across demographic subgroups.