Low birth weight (BWT) may contribute to kidney disease and could explain some of the variance in the development of early diabetic kidney disease. This hypothesis was tested in the multicenter SEARCH study (3,714 youth with diabetes <20 years of age). A morning spot urine sample, laboratory and anthropometric data, and a medical history were obtained. Elevated albumin to creatinine ratio (ACR) was defined as > or =30 mcg albumin/mg creatinine, and BWT was categorized as low (<2,500 g), reference (2,500-4,000 g), or high (>4,000 g). The relationship of BWT to elevated ACR was analyzed using multiple logistic regression. In youth with diabetes, the prevalence of elevated ACR was 12.6% in those with low BWT, 9.7% in those with reference BWT, and 8.9% in those with high BWT. BWT category was not significantly associated with elevated ACR (p = 0.23). Those with diabetes duration >18 months (2,032) had the following association of BWT category with elevated ACR [odds ratio (OR) = 1.64, 95% confidence interval (CI) 1.00-2.69, p = 0.0503] for low BWT compared with reference BWT. Whereas low BWT may be a factor in kidney disease, little evidence was found of a relationship between low BWT and elevated ACR in this study population of youth with diabetes.