The first pharmacokinetic data are reported of azlocillin injected intramuscularly to adult probands. The blood serum and urinary levels of azlocillin were determined microbiologically in 8 healthy volunteers after intramuscular injection of 2 grams. Peak serum levels of azlocillin were found by the end of hour 1 after injection, average level was (55.06 +/- 10.25) mg/l. At hour 2 the average level was (33.64 +/- 6.46) mg/l. and at hour 4, (9.47 +/- 1.79) mg/l. The biological half-life was 1.4 hour. In urine, (41.2 +/- 7.7)% of the administered dose was eliminated within 8 hours on average.