Clonidine hydrochloride (CH) is an antihypertensive drug with complex pharmacologic activity including central and peripheral alpha-adrenergic stimulation and CNS depression. We reviewed the records of 5 children admitted to our Pediatric Intensive Care Unit following accidental ingestion of CH. All patients presented with lethargy or stupor, beginning 20-60 minutes after ingestion. Respiratory depression or apnea occurred in 4, requiring endotracheal intubation in 2 and mechanical ventilation in 1. All 5 developed mild to moderate hypertension, and 3 developed asymptomatic bradycardia. The dose of CH ingested was estimated to be 0.2-0.4 mg in 4 out of 5 patients. Treatment consisted of efforts to prevent absorption of CH from the GI tract and supportive care. All signs of CH toxicity resolved within 6-14 hours. Four patients were transferred from ICU within 24 hours and discharged home the following day. One patient developed post-extubation stridor and atelectasis. Significant toxicity occurred even though the amount of CH ingested was relatively small in at least 4 or 5 patients. Transient hypertension occurred early in the hospital course of all patients and resolved without treatment. Hypotension and symptomatic bradycardia were not observed. Apnea was the most serious abnormality observed. All patients recovered without significant morbidity.