The long-term kidney function (KF) in the three categories of diabetic type 1 pancreas (P) transplant recipients (simultaneous P and kidney [SPK]; P after K [PAK]; PTx alone [PTA] was studied sequentially over a 2-year period in 62 patients who received a bladder-drained allograft that functioned for at least 1 year. Fifty-three (85%) patients were analyzed at 1 month, 42 (68%) at 1 year, and 16 (26%) at 2 years posttransplant. Comparison of KF was made within each recipient category and between categories. In addition, the KF in the SPK and PAK patients was compared to a matched group of diabetic type 1 recipients of KTx alone (functioning at least 1 year). In the SPK group, KF was stable over time: the mean +/- SD serum creatinine (mg/dl) was 1.5 +/- 0.5 at 1 month, 1.8 +/- 1.0 at 1 year, and 1.7 +/- 0.5 at 2 years. In the PAK category, the pre-PTx serum creatinine value was 1.4 +/- 0.5, and then remained stable after the PTx (1.3 +/- 0.2 at 1 month, 1.3 +/- 0.4 at 1 year, and 1.2 +/- 0.4 at 2 years). In the recipients of a PTA, the values at 1 month (1.1 +/- 0.4), 1 year (1.4 +/- 0.5), and 2 years (1.3 +/- 0.5) were significantly higher (P less than or equal to 0.03) than the pre-PTx value (0.9 +/- 0.2); and results at 1 month and 2 years were lower than those at 1 year, a significant difference compared to the 1-month value (P = 0.01). Comparisons between the categories of PTx recipients demonstrated that the pre-PTx value in the PTA group (0.9 +/- 0.2) was significantly lower (P = 0.01) than in the PAK group (1.4 +/- 0.5). At 1 month the serum creatinine value in the PTA category (1.1 +/- 0.4) was significantly lower (P = 0.02) than in the SPK category (1.5 +/- 0.5), but thereafter (1 and 2 years) the difference was not significant (P greater than 0.1). KF in recipients of KTx alone was similar at each post-Tx time point when compared to the SPK and PAK categories. We concluded that a PTx can be performed in diabetics without a detrimental effect on a simultaneously or a previously transplanted kidney and that a statistically significant, albeit minimal to moderate, initial but not progressive deterioration in native KF occurs in recipients of a PTx alone.