This report presents 6 cases of acute lithium intoxication that were treated over the past 10 years. The range of the lithium overdose was 2,800 mg to 16,800 mg, and the overdose in all cases was greater than 40 mg/kg, which is the dose considered to induce lithium intoxication. The lithium serum concentration of two cases was greater than the lethal concentration (4 mmol/l). One of the two cases was treated with continuous hemodiafiltration (CHDF). The serum lithium concentration of the patient without CHDF gradually decreased and remained at a supranormal range of 36 hours after the treatment. On the other hand, the serum lithium level of the case with CHDF rapidly decreased and it finally reached the therapeutic level, and no post-dialysis rebound effect in the lithium concentration was detected. The serum lithium concentration cannot be easily measured in the clinical setting and the patient's conditions are not always in line with the serum lithium concentration. Therefore, in cases with toxic serum concentration or when an amount greater than 40 mg/kg of lithium is taken, CHDF may provide the most effective clearance of lithium from the circulation.