In five symptomatic patients with acute quinine poisoning the mean admission plasma concentration was 11.1 mg l-1. After treatment with repeated oral charcoal 50 g 4 hourly, plasma quinine concentrations fell rapidly with a mean half-life of 8.1 +/- 1.1 h (s.d.) compared with more than 24 h in a previous report in similarly poisoned patients. The visual impairment which was expected in a patient with cardiotoxicity and a plasma quinine concentration of 12.6 mg l-1 did not occur, but late treatment with charcoal was of no obvious benefit in another patient who was already blind. Repeated oral charcoal has been shown to increase the rate of elimination of a therapeutic dose of quinine in healthy volunteers. It appears to be the only practical means of enhancing the removal of this drug after overdosage and should reduce the risk of potentially disastrous complications.