Chronic allograft nephropathy (CAN) is usually progressive and its natural course can only be modified at the initial stages. In this study, we classified Tc-99m DTPA renal scintigraphy findings in respect to perfusion/uptake pattern and correlated these findings with different grades of CAN. The aim was to define scintigraphic parameters which help to guide therapy at early stages of CAN. This study included 50 renal allograft recipients with biopsy proven CAN. For renal scintigraphy, every recipient received an intravenous injection of 259-333 MBq of Tc-99m DTPA. A renal time-activity curve based on extrarenal background-corrected data has been used for evaluation of perfusion and function. Quantitative evaluation of perfusion included calculation of the ratio of peak perfusion counts divided by plateau counts (P:PL). Deterioration of renal function was accompanied with a gradual loss of peak and plateau pattern. For the evaluation of uptake in relation to perfusion pattern, we have graded the renogram curves into 4 based on the presence of peak and plateau pattern and the presence of an uptake peak. In patients with CAN, the mean P:PL was significantly lower than that of the control group. Although peak to plateau pattern was preserved in low-grade CAN, this pattern was lost in the later stages. The gradual changes in different grades of CAN in respect to uptake/perfusion pattern was a gradual loss of peak and plateau pattern followed by a decline in uptake. In recipients with high-grade CAN, there was a flat curve with no uptake peak. Evaluation of Tc-99m DTPA time-activity curves revealed a progressive change in perfusion/uptake pattern in patients with CAN. According to our results, deterioration of perfusion preceded the decline in uptake. The implications of these results on the pathophysiology and the management of CAN need to be determined.