The pharmacokinetic properties of cefodizime, a new aminothiazolyliminomethoxycephalosporin, were studied in laboratory animals and compared with the pharmacokinetics of another long-acting cephalosporin, ceftriaxone. Both cephalosporin derivatives showed high affinity (33-99%) for serum proteins. High and prolonged blood respectively serum levels of the antibiotics were achieved following subcutaneous and intravenous injection into mice, rats, rabbits, dogs and monkeys. Cefodizime elimination half-lives ranged from 1.17 hours in mice to 3.53 hours in rabbits compared to ceftriaxone half-lives ranging from 0.73 hour in mice to 7.31 hours in rabbits. The antibiotics were well distributed in the body and penetrated into tissues and body fluids to a high degree. Particularly high and prolonged levels were detected in the lungs, liver and kidneys of the experimental animals. Large amounts, approximately 35-55% of the given dose, were recovered in the urine of rabbits and dogs, while the recovery rate in the bile of rabbits was only 0.57% for cefodizime and 1.08% for ceftriaxone.