Acute renal failure is a recognized manifestation of paracetamol toxicity, but comparatively little data is available concerning its onset and duration. The present study sought to characterize the time course of rising serum creatinine concentrations in paracetamol nephrotoxicity. Renal failure was defined by serum creatinine concentration >or=150 micromol/L (1.69 mg/dL) or >or=50% increase from baseline. Serum creatinine concentrations and alanine aminotransferase activity were considered with respect to the interval after paracetamol ingestion. There were 2068 patients with paracetamol overdose between March 2005 and October 2007, and paracetamol nephrotoxicity occurred in 8 (0.4%). All had significant hepatotoxicity, and peak serum alanine aminotransferase activity occurred at 2.5 days (2.2 to 2.9 days) after ingestion. Peak serum creatinine concentrations did not occur until 5.5 days (4.4 to 5.9 days) after ingestion (p = .031 by Wilcoxon test). Serum creatinine concentrations slowly restored to normal, and renal replacement was not required. In this patient series, rising serum creatinine concentrations only became detectable after more than 48 hours after paracetamol ingestion. Therefore, renal failure might easily be missed if patients are discharged home before this. Further work is required to establish the prevalence of paracetamol-induced nephrotoxicity, and its clinical significance.