Objective : This paper presents data from a retrospective study of endoscopic third ventriculostomy (ETV) in patients with shunt malfunction and proposes a simple and reasonable post-operative protocol that can detect ETV failure. Methods : We enrolled 19 consecutive hydrocephalus patients (11 male and 8 female) who were treated with ETV between April 2001 and July 2010 after failure of previously placed shunts. We evaluated for correlations between the success rate of ETV and the following parameters : age at the time of surgery, etiology of hydrocephalus, number of shunt revisions, interval between the initial diagnosis of hydrocephalus or the last shunt placement and ETV, and the indwelling time of external ventricular drainage. Results : At the time of ETV after shunt failure, 14 of the 19 patients were in the pediatric age group and 5 were adults, with ages ranging from 14 months to 42 years (median age, 12 years). The patients had initially been diagnosed with hydrocephalus between the ages of 1 month 24 days and 32 years (median age, 6 years 3 months). The etiology of hydrocephalus was neoplasm in 7 patients; infection in 5; malformation, such as aqueductal stenosis or megacisterna magna in 3; trauma in 1; and unknown in 3. The overall success rate during the median follow-up duration of 1.4 years (9 days to 8.7 years) after secondary ETV was 68.4%. None of the possible contributing factors for successful ETV, including age (p=0.97) and the etiology of hydrocephalus (p=0.79), were statistically correlated with outcomes in our series. Conclusion: The use of ETV in patients with shunt malfunction resulted in shunt independence in 68.4% of cases. Age, etiology of hydrocephalus, and other contributing factors were not statistically correlated with ETV success. External ventricular drainage management during the immediate post-ETV period is a good means of detecting ETV failure.