Ultrafiltrate and total plasma and cerebrospinal fluid (CSF) platinum concentrations were examined in a patient with neuroblastoma following a 2-hour infusion of 120 mg/m2 of cisplatin. Total plasma platinum was 93.4% bound, while the ultrafiltrate of plasma accounted for the remaining 6.6%. The CSF ultrafiltrate resulted in equivalent concentrations of platinum to total CSF platinum. CSF concentrations were 2.9% of the total plasma platinum and 43.5% of the ultrafiltrate plasma platinum 2 hours after the end of the infusion.