Introduction: Alkaline Phosphatase (ALP) is a group of 4 isoenzymes produced in different tissues. Elevated levels of ALP can be developed under physiological conditions, and can indicate the presence of bone or hepatobiliary diseases. In children, one of its most common harmless causes is benign transient hyperphosphatasemia (BTH), a little known condition. The objective is to report BTH cases and propose a monitoring plan. Case reports: The cases of 5 children aged between 11 and 50 months are presented, 4 of them female, with the incidental finding of a sudden and severe ALP elevation (> 1,000 U/l), in tests ordered due to either abnormal growth and development, or intercurrent infections. Bone and liver disease were ruled out using the patient history, physical examination and basic laboratory results. Isoenzymes levels were determined in 2 patients. A return to normal ALP levels was observed over a period of 1-6 months, with no evidence of further complications. Conclusion: BTH is a benign self-limiting biochemical disorder, which should be considered in children under 5 years old with severe ALP elevation in the absence of clinical or laboratory abnormalities suggestive of bone or liver disease.