The concentration-profile of the antineoplastic agent carboplatinum in serum and intraperitoneal-fluid (IPF) of six female patients was studied. Pharmacokinetical analysis showed a rapid distribution-phase between both compartments within the first 4h after administration (t1/2 serum = 4.4 h, t1/2 IPF = 3.3 h). Elimination half-life of carboplatinum of 20.3 h from the blood-vessel-system was significantly higher than from the intraperitoneal-compartment (t1/2 = 10.6 h). The relative bioavailability (calculated as AUC-values) was at least 6 times higher for the IPF than for serum within the first 48 h. 98% of measured amount were eliminated from both compartments within this time. The desired high IPF-levels support this route of administration.