To determine the impact of neutropenia on the pharmacokinetics of meropenem, 14 patients with fever and neutropenia were given 1 g of meropenem i.v. every 8 h as an infusion over 30 min. The volume of distribution (16.2 1/1.73 m2) and the nonrenal clearance [75 ml/(min x 1.73 m2)] in this group were significantly increased compared to healthy subjects studied previously with identical techniques. The kinetic study was repeated when the patients had a normal temperature and a raised neutrophil count; most kinetic variables did not differ from the findings on the first day of treatment. The pharmacokinetic profile of meropenem in febrile neutropenic patients differs from earlier findings in healthy subjects. Considering these data and known minimum inhibitory concentration values for common pathogens, meropenem administered every 6 to 8 h seems an appropriate regimen in patients with febrile neutropenia. The shorter time interval may be used for treatment ofPseudomonas infection.