The pharmacokinetics of a 440 mg iv dose of teicoplanin were studied in six male volunteers. The levels of the compound were measured microbiologically in serum, blister fluid and urine. The mean serum level 0-5 h after injection was 44.6 mg 1(-1), falling to 3.6 mg 1(-1) at 49 h. The serum elimination half-life of teicoplanin when fitted to a two-compartment model was 34.2 h; a three-compartment model gave a longer half-life. The apparent distribution half-life was 1.5 h. Penetration into cantharides induced blister fluid was moderately fast, the mean maximum concentration (14.8 mg 1(-1)) occurring at 2.7 h, the mean percentage penetration being 77.4%. Urinary recovery of the drug was 48.3% by 96 h. The drug penetrated rapidly into the non-inflammed peritoneal fluid of 34 patients undergoing elective surgery. The percentage penetration being 40% within the first hour, and 94.6% over the period of the study.