The serum concentration-time profiles of cetirizine were measured in 8 male end-stage renal failure (ESRF) patients on chronic hemodialysis (HD). Cetirizine (5 mg) was ingested three times a week during the predialysis period. Blood samples were drawn for basal level evaluation, before and after dialysis on 3 days per week, and before HD the following week. The serum levels of cetirizine were measured using a validated atmospheric-pressure ionization liquid chromatography-tandem mass spectrometry method. Basal levels of cetirizine in HD patients were confirmed to be 0 ng/ml. The predialysis levels of cetirizine on days 1, 3, 5, and 8 were (mean ± SD) 2.74 ± 7.76, 34.16 ± 21.55, 35.58 ± 13.43, and 22.47 ± 12.92 ng/ml, respectively. The postdialysis levels of cetirizine 4–5 h after ingestion were as follows (ng/ml): day 1, 103.11 ± 37.27; day 3, 131.34 ± 51.18, and day 5, 136.48 ± 48.72. Between dialysis sessions, no supplemental dosage was required to keep the therapeutic range of 14 ng/ml. In addition, the predialysis levels on day 8 were not statistically different from the basal levels. Evidence from the multiple-dose study supports the clinical use of cetirizine for ESRF patients on HD. Thus, it is concluded that a prescription of 5 mg cetirizine three times a week during the predialysis period will be the effective and safety renal dosage for ESRD patients on HD.