Audiometric changes following quinine administration were studied in healthy Caucasian subjects and patients suffering from falciparum malaria disease. Quinine-dihydrochloride was administered intravenously as a single dose of 300 mg to 12 healthy subjects and as multiple doses of 600 mg in 4 h every 8 h in 10 Plasmodium falciparum malaria patients. The hearing function was monitored by conventional and high frequency audiometry. In nine healthy subjects hearing loss was documented at 2-4 h after infusion of Quinine-dihydrochloride at a mean maximal plasma quinine concentration of only 2 mg/l. In one healthy subject a persistent loss occurred of 20 dB at 14 kHz in one ear. In all malaria patients severe hearing losses and adverse effects related to ototoxicity were documented, but all the audiograms had returned to normal after 1 week and side effects disappeared. This study has shown that ototoxicity induced by quinine is almost completely reversible in healthy volunteers and in malaria patients.