The pharmacokinetics of temocillin, a new semisynthetic parenteral penicillin, were studied in 10 healthy volunteers. Doses of 0.5, 1.0, and 2.0g were administered by intravenous bolus injection at weekly intervals, and serum and urine samples were assayed by an agar diffusion method. Mean peak serum concentrations were: 77.9 (± 28.4) mg/L (0.5g), 160.8 (± 58.2) mg/L (1.0g), and 236.1 (± 93.3) mg/L (2.0g), with serum concentrations still being measurable after 12 hours for all doses [7.9 (± 3.7) mg/L, 12.9 (± 5.2) mg/L, 14.8 (± 6.3) mg/L]. According to a 2-compartment open model, the mean terminal half-lives of 0.5, 1.0, and 2.0g doses were 5.2 (± 0.3), 5.0 (± 0.2), and 5.0 (± 0.2) hours, respectively. The total volume of distribution averaged 0.15 (± 0.01), 0.17 (± 0.01), and 0.24 (± 0.01) L/kg bodyweight, respectively, mean renal clearances were 18.5 (± 3.2), 19.6 (± 5.0), and 29.8 (± 2.6) ml/min, respectively, and the area under the serum concentration time curve (AUC) was 344.1 (± 18.7), 573.3 (± 27.8), and 784.5 (± 47.1) mg · h/L, respectively. At 74 (± 12.9)%, the 24-hour urinary recovery was highest for the low dose, followed by 68.1 (± 6)% for the 2.0g dose, and 66.1 (± 16.8)% for the 1.0g dose. No untoward side effects were recorded. Thus, temocillin appears to be a penicillin with a prolonged half-life and high AUC.