Whether early glomerular, tubulointerstitial, vascular, and global glomerulosclerotic lesions can predict progression of diabetic nephropathy is not well defined. Here, we sought to determine whether renal structural parameters predict the development of proteinuria or ESRD after long-term follow-up. We measured several renal structures in kidney biopsies from 94 normoalbuminuric patients with longstanding type 1 diabetes using unbiased morphometric methods. Greater width of the glomerular basement membrane and higher levels of glycated hemoglobin were independent predictors of progression to diabetic nephropathy in this normoalbuminuric cohort. Moreover, none of these patients with type 1 diabetes who had glomerular basement membrane widths within the normal range developed proteinuria and/or ESRD. In conclusion, careful quantitative assessment of kidney biopsies in normoalbuminuric patients with type 1 diabetes adds substantially to the prediction of progression to clinical diabetic nephropathy.