OBJECTIVE-To evaluate whether etiologic diabetes type is associated with the degree of albuminuria in children with diabetes. RESEARCH DESIGN AND METHODS-SEARCH is an observational, longitudinal study of children with diabetes. Youth with newly diagnosed diabetes were classified according to diabetes autoantibody (DAA) status and presence of insulin resistance. We defined insulin resistance as an insulin sensitivity score <25th percentile for the United States general youth population.DAA statuswas based on positivity for the 65-kD isoformof glutamate decarboxylase and insulinoma-associated protein 2 antigens. The four etiologic diabetes type groups were as follows: DAA+/insulin-sensitive (IS) (n = 1,351); DAA+/insulin- resistant (IR) (n = 438); DAA-/IR (n = 379); and DAA-/IS (n = 233). Urinary albumin:creatinine ratio (UACR) wasmeasured froma random urine specimen. Multivariable regression analyses assessed the independent relationship between the four diabetes type groups and magnitude of UACR. RESULTS-Adjusted UACR means across the four groups were as follows:DAA +/IS = 154μg/mg; DAA+/IR = 137 μg/mg; DAA -/IR = 257 μg/mg; and DAA-/IS = 131 μg/mg (P < 0.005). Only DAA-/IR was significantly different. We performed post hoc multivariable regression analysis restricted to the two IR groups to explore the contribution of DAA status and insulin sensitivity (continuous) to the difference in UACR between the IR groups. Only insulin sensitivity was significantly associated with UACR (β = 20.54; P < 0.0001). CONCLUSIONS-In youth with diabetes, the DAA-/IR group had a greater UACR than all other groups, possibly because of the greater magnitude of insulin resistance. Further exploration of the relationships between severity of insulin resistance, autoimmunity, and albuminuria in youth with diabetes is warranted.