Background: Animals treated with gentamicin can show residual areas of interstitial fibrosis in the renal cortex. This study investigated the expression of nuclear factor-ĸB (NF-ĸB), mitogen-activated protein (MAP) kinases and macrophages in the renal cortex and structural and functional renal changes of rats treated with gentamicin or gentamicin + pyrrolidine dithiocarbamate (PDTC), an NF-ĸB inhibitor. Methods: 38 female Wistar rats were injected with gentamicin, 40 mg/kg, twice a day for 9 days, 38 with gentamicin + PDTC, and 28 with 0.15 M NaCl solution. The animals were killed 5 and 30 days after these injections and the kidneys were removed for histological and immunohistochemical studies. The results of the immunohistochemical studies were scored according to the extent of staining. The fractional interstitial area was determined by morphometry. Results: Gentamicin-treated rats presented a transitory increase in plasma creatinine levels. Increased ED-1, MAP kinases and NF-ĸB staining were also observed in the renal cortex from all gentamicin-treated rats compared to control (p < 0.05). The animals killed on day 30 also presented fibrosis in the renal cortex despite the recovery of renal function. Treatment with PDTC reduced the functional and structural changes induced by gentamicin. Conclusions: These data show that inhibition of NF-ĸB activation attenuates tubulointerstitial nephritis induced by gentamicin.