The authors report on the pharmacokinetic profile of a new analgesic, meptazinol, from studies of plasma and urine levels after intravenous injection in 4 healthy volunteers. Conjugated product is formed very soon after injection and its concentration changes little over the period studied compared with the unchanged product where a fast, then a relatively slow phase of decline can easily be distinguished, suggesting a two compartment open system model. Meptazinol is predominantly eliminated in this conjugated form by urinary excretion of the metabolites. Excretion is very rapid in the first few hours after dosing and elimination is almost completed after 24 hours.