The presence of persistently elevated urinary concentrations of protein or albumin is considered a sign of kidney damage. The diagnosis and staging of chronic kidney disease (CKD) is nowadays based upon the presence of signs of kidney damage together with the estimation of the glomerular filtration rate.The presence of either proteinuria or albuminuria identifies a group of patients with higher risk of CKD progression and higher cardiovascular risk. Treatment with angiotensin converting enzyme inhibitors or angiotensin-receptor blockers,for instance, decreases both the progression of CKD and the incidence of cardiovascular events and death in patients with CKD and proteinuria. Thus, proteinuria is currently considered a therapeutic target by itself. Despite of the importance of detecting and monitoring proteinuria in the diagnosis and follow-up of CKD, there is not a consensus among the clinical practice guidelines published by different scientific societies on the diagnostic cut-off levels, on different sampling procedures,on the units used in laboratory reports or just on whether it should be defined in terms of albumin or proteinuria. The goal of this document, created by the consensus of the Spanish Society of Clinical Biochemistry and Molecular Pathology(SEQC, representing its spanish acronym) and the Spanish Society of Nephrology (S.E.N.), is to recommend to medical and laboratory clinicians appropriate guidelines for the detection and monitorization of proteinuria as a marker of CKD in adults and children. These recommendations result from searching,evaluating and summarizing current scientific evidence published in the last years.