We recently reported that transient appearance of interstitial myofibroblasts and infiltrating macrophages might play a role in cellular recovery in uranyl acetate (UA)-induced acute renal failure (ARF). Here we tested the effects of mycophenolate mofetil (MMF), which attenuates infiltration of lymphocytes, macrophages, and myofibroblasts, but does not suppress epithelial regeneration, on renal tissue repair. Rats treated with MMF (20 mg/kg/day) or vehicle were sacrificed at 2, 5, and 7 days after induction of ARF by injection of 5 mg/kg UA. Renal tissues were immunostained for bromodeoxyuridine (BrdU) and Ki67, alpha-smooth muscle actin (alpha-SMA), ED1, and CD43. The expression levels of alpha-SMA mRNA were examined by reverse transcription-polymerase chain reaction. Body weight loss or serum albumin levels were similar in MMF and vehicle rats during the experiment. In vehicle group, serum creatinine (Scr) significantly increased after day 5, but proximal tubular (PT) damage score increased as early as day 2 after UA injection. BrdU- or Ki67-positive regenerating tubular cells, ED1-positive macrophages and alpha-SMA-positive myofibroblasts significantly increased in the interstitium after day 5. In MMF-treated rats, Scr and PT damage score significantly increased at day 7 and the number of regenerating PT were significantly reduced compared with vehicle-treated rats at days 5 and 7. The numbers of macrophages and myofibroblasts and the expression of alpha-SMA mRNA were significantly lower in MMF than in vehicle rats at day 5, indicating that reduced interstitial cellular response is linked to the inhibition of regenerative repair. CD43-positive lymphocytes were significantly reduced in MMF group than in vehicle group at day 7, suggesting that lymphocyte infiltration does not seem to contribute to early regenerative response of proximal tubules. The transient appearance of myofibroblasts and macrophages in the interstitium may promote regenerative repair in UA-induced ARF in rats.