BACKGROUND We evaluated the effect of oral clonidine on postoperative vomiting (POV) in children undergoing strabismus surgery. METHODS Eighty ASA physical status I children aged 3-12 years were randomly assigned to one of two groups in a double-blinded manner. One hour before surgery, each patient in the clonidine group (n=40) received clonidine 4 micro g kg-1 in apple juice 0.2 ml kg-1, and each of the controls (n=40) received apple juice 0.2 ml kg-1 only. The protocol for general anesthesia was propofol-sevoflurane in N2O/O2. A paracetamol suppository was administered in each case to prevent postoperative pain. Patient responses during 0-48 h after anesthesia were recorded as complete (no POV, no antiemetic rescue required), retching, vomiting, or rescue antiemetic. RESULTS There were no significant differences between the clonidine and control groups regarding the number of patients with complete response (21 vs. 18, respectively) retching (10 vs. 14, respectively), vomiting (19 vs. 22, respectively), or rescue antiemetic (9 vs. 12, respectively) during the first 48 h. CONCLUSIONS Oral premedication with clonidine 4 micro g kg-1 did not reduce the rate of POV in the children undergoing strabismus surgery.