Asymptomatic proteinuria is a common finding in primary care practice. Most children with asymptomatic proteinuria, diagnosed at screening urinalysis, do not have kidney disease. When proteinuria is detected, it is important to determine whether it is transient, orthostatic or persistent. Transient proteinuria is most often associated with fever, exercise or stress and it resolves on urine testing when the cause is withdrawn. Orthostatic proteinuria is a benign and common condition in school-age children. Persistent proteinuria should be carefully evaluated because it is a marker of renal damage and associated with kidney disease. It is not necessary to extensively investigate all children found to have proteinuria. Children with persistent proteinuria should be referred to a pediatric nephrologist to get a diagnosis and start treatment when necessary.