The child Supplemental Security Income (SSI) caseload increased by nearly 40 percent between 2002 and 2012, from just over 900,000 to nearly 1,300,000, and the upward trend shows no signs of reversing. In this descriptive paper, we explore the nature of the caseload growth over this period. Consistent with previous studies, we find that national trends in child SSI participation are driven by growth in cases diagnosed with mental impairments, which more than doubled over this period. Our state-level analysis reveals that the national trends mask significant variation across states. Some states experienced only very small increases, while other states experienced dramatic increases, the largest percentage increase being in Texas, where the mental diagnoses caseload increased by 129 percent over this 10-year period. Our focus on states suggests that the experience is varied and no small set of factors can explain the differential growth across states. In particular, we do not find evidence of an aggregate relationship between changes in state-level diagnosis rates among the general population of children and new SSI cases. The data offer some suggestion that rates of growth in special education participation at the state level lead to increases in new child SSI cases. More specifically, the data point to the need for in-depth case studies of caseload growth in key states such as Arkansas, the District of Columbia, and Texas.