Proteinuria in children with chronic kidney disease (CKD) is common and its etiology differs from that in adults. How proteinuria influences the rate of progression of CKD has been analyzed in multiple retrospective clinical studies and more recently in a few prospective ones. In this review I summarize the results, strengths and weaknesses of each of these studies. The findings of several retrospective studies in children with CKD have confirmed what we have learned from adult studies on the association between proteinuria and worsening kidney function. Larger prospective clinical studies have examined the effects of proteinuria on the rate of decline of kidney function and the risk of end-stage kidney disease. They have also considered children with glomerular and, more importantly, the more common, congenital causes of CKD. Current studies have important strengths but also a few weaknesses that limit the validity of the conclusions which can be drawn. There is still a need for large clinical trials that focus primarily on studying the influence of proteinuria on kidney function and on finding remedies that delay progression.