We report 20 children diagnosed with transient benign hyperphosphatasemia (THI) during a period of 2 years. The mean age was 29.3 months, ranging from 3 months to 10.2 years, with a male predominance (1.5:1). There were several associated disorders, with the most frequent being acute gastroenteritis, failure to thrive and asthma, the mean alkaline phosphatase (AP) value was 4,137 +/- 2,624 U/L (mean +/- SD). All AP values were above the 97th percentile for each age, with a mean of 3.8 times the level in the 97th percentile for every one-year period (between 0 and 14 years), 6.2 times the 50th percentile mean level and 14.8 times higher than the mean normal upper limit value for adults. The range was from 1,199 to 9,950 U/L. Their serum AP levels returned to normal in a mean period of 3.16 months (1 to 6 months) i 18 cases. The remaining 2 cases are pending on a new checkup. There was no seasonal predominance and the frequency was uniform throughout the year In 2 cases the onset age was more than 5 years and in another 2 patients follow-up serum AP levels did not return to reference values within 4 months. THI is a benign and self-limited entity. We think that the age and duration limits proposed by Kraut may be too rigorous; hence, it would be advisable to review these criteria.