Amodiaquine hydrochloride (3 mg base kg‐1) was given by constant rate intravenous injection over 10 min to seven healthy adult male volunteers, and by constant rate infusion (10 mg base kg‐1) over 4 h to 10 adult patients admitted to hospital with falciparum malaria. After intravenous injection in volunteers there was considerable variation in plasma concentration profiles between subjects; peak plasma concentrations ranged between 65 and 1921 ng ml‐1. A biexponential equation was fitted to the plasma concentration time data and the following estimated pharmacokinetic parameters (geometric mean; range) were derived; lambda 1 = 24.4 (7.6‐95.0) h‐1, lambda 2 = 0.33 (0.12‐ 0.79) h‐1, V1:1.1 (0.3‐3.6) 1 kg‐1, Vss: 17.4 (2.3‐95.9) 1 kg‐1 and systemic clearance 13.0 (4.7‐56.6) 1 kg‐1 h‐1. After intravenous infusion there was also considerable variability between patients with post‐infusion plasma concentrations ranging between 82 and 836 ng ml‐1. The plasma concentration‐time profiles were biphasic with the following estimated pharmacokinetic parameters (geometric mean; range) alpha = 1.87 (0.60‐8.52) h‐1, beta = 0.069 (0.021‐0.265) h‐1, V1: 4.6 (0.5‐ 29.3) 1 kg‐1, Vss: 38.3 (3.7‐127.9) 1 kg‐1 and systemic clearance CL (1.6‐17.3) 1 kg‐1 h‐1. There was no measurable long terminal elimination phase, and the principal metabolite desethyl amodiaquine was not detected in the plasma samples. There was no serious toxicity in either group. During intravenous injection there was a significant fall in systolic blood pressure in four subjects (mean fall 16 mm Hg) but there was no significant change in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)