Objective: To sum up the causes of recurrence of chronic subdural hematoma (CSDH) from failure of trepanation and drainage and explore its prevention and treatment.Methods: From October 1988 to June 2002 a total of 358 patients with CSDH were treated with trepanation and drainage in our hospital. Among them 15 patients had recurrence of CSDH after operation. The data of the 15 patients were reviewed retrospectively.Results: Of the 15 patients, 13 were cured by retrepanation and redrainage, one cured by removal of hematoma by craniotomy with bone flap, and one, a 1-year old child, gave up reoperation due to severe encephalatrophy. Conclusions: Most CSDHs which recur after trepanation and drainage can be cured by retrepanation and redrainage. For the patients with repeated recurrence of CSDH removal of hematoma capsule can be considered. The causes of recurrence of CSDH are related to disease course, the thickness of hematoma capsule, the severity of encephalatraphy and whether the hematoma cavity is drained or irrigated completely, and operation methods.