We present a 4-year-old girl with allergies and asthma who developed night terrors after initia- tion of montelukast at 2 years of age. Montelu-kast was discontinued and cetirizine was started. Nigh terrors persisted. Sleep diaries were col- lected and diagnosticpolysomnogram (PSG) was ordered. Sleep diaries revealed an average sleep time of 10 hours with night terrors occur- ring three nights a week approximately two hours after sleep onset. The PSG did not show evidence of sleep disordered breathing or peri- odic leg movements. Cetirizine was discontin- ued and the night terrors ceased. Upon re-intro- duction of the medication, the sleep terrors re- curred.