Eight children (3.84 +/- 1.17 years old) received a single oral 5 mg cetirizine dose (0.32 +/- 0.07 mg.kg-1) as a 10 mg.ml-1 solution, 1.73 (+/- 0.64) hours before a minor surgical intervention (mean duration +/- SD = 0.90 +/- 0.25 h). Seven venous blood samples were collected before administration (t0) and 0.5 h, 1.5 h, 4 h, 8 h, 12 h and 24 h after dosing, and urine samples were collected up to 24 hours after the dose. The mean +/- SD kinetic parameters were: peak plasma level (Cmax) 607 +/- 231 micrograms.l-1 reached in 1.93 +/- 1.39 h (tmax), elimination half-life (t1/2) 5.55 +/- 0.98 h, area under the plasma concentration time curve (AUC0-infinity) 4,772.1 +/- 1,318.4 micrograms.l-1.h, mean residence time (MRT) 8.13 +/- 1.31 h, apparent plasma clearance (Cl/f) 1.27 +/- 0.80 ml.min-1.kg-1, apparent volume of distribution (Vz/f) 0.60 +/- 0.38 l.kg-1. Urinary recovery was 38.4 +/- 9.9% (n = 4) of the dose. Renal clearance was 0.42 +/- 0.10 ml.min-1.kg-1 (n = 6). No influence of age on the cetirizine parameters was evidenced among this group, except for MRT (p < 0.05) which decreases with age. When compared with results in adults, elimination half-life (t1/2) was twice as short and apparent clearance twice as great. These results suggest that a higher dosage b.i.d. may be required in children.