The present study was performed in order to identify the cost of drugs used without documenting them in the patients' file and the wastage of drugs in a pediatric anesthesiology ward. In a prospective, blinded, observational design, drug utilization of 610 consecutive patients, undergoing an elective or emergency surgical procedure was evaluated. The number of undocumented drugs per 100 requested units and the number of wasted drugs per 100 requested units were computed and multiplied by its corresponding unitary cost. The median undocumented cost was 92.4 US dollars (95% CI 17.2-216.6 dollars) per 100 requested units. Succinylcholine (40 mg/2 mL) was the main undocumented drug; its use was not documented in approximately 50% cases in which this neuromuscular blocking agent was requested. However, rocuronium and nalbuphine had the highest unjustified cost, 770.6 dollars and 847.0 dollars per 100 requested units, respectively. Ketorolac, diclofenac, metamizol, furosemide, methylprednisolone, sodium bicarbonate, and cisatracurium were requested and documented. The median cost of wasted drug was 141.8 dollars (95% CI 55.8-448.2 dollars) per 100 requested drugs. More than 80% of adrenaline, naloxone, flunitrazepam, ephedrine, and cisatracurium were wasted. However, the highest cost of wasted drugs was for ondansetron, cisatracurium, methylprednisolone, and rocuronium. The uncontrolled availability and use of drugs may represent an important amount of resources wasted without any awareness of the staff in a department of pediatric anesthesia.