To evaluate the usefulness of a concurrent nighttime morphine infusion in pediatric patient-controlled analgesia (PCA), 36 school-age children undergoing elective lower extremity surgery were randomly assigned to receive morphine by PCA alone, or PCA with a nighttime infusion of morphine (PCA+BI). Postoperatively, patients breathed air and had oxygen saturation recorded continuously for the duration of PCA use. Total morphine requirements were decreased in the PCA group as compared to PCA+BI patients. PCA pump activation, VAS pain, and sedation scores were similar between the two groups at all times. Compared to the PCA group, patients assigned to the PCA+BI group spent more time with SpO2 of 90% or less, during the nighttime infusion (P < 0.05). The use of a nighttime infusion of morphine did not appear to offer any advantage over the use of PCA alone in this patient population.