Urinary kallikrein excretion is known to increase in patients with nephrotic syndrome and sick cell disease, but decrease in patients with chronic kidney disease or uremia. Some of authors consider urinary kallikrein is a marker of nephropathy. To evaluate the possible role of kallikrein kinin system in chronic kidney disease, we conduct a retrospective longitudinal observation study. Patients who participating in the “Efficacy of Pentoxifylline on Chronic Kidney Disease” study are included in the study. The morning spot urinary kallikrein and cytokines are measured at the time point of 0 and 12 month in addition to clinical parameters. The correlation of urinary kallikrein and cytokine concentration will be evaluated. Using multiple regression model, the relationship of urinary kallikrein excretion with degree of proteinuria, creatinine clearance and other clinical parameter will also be evaluated.