Three children, ages 6 months, 13 months and 10 years were treated by exchange transfusions following exposure to methylmercury in the Iraq outbreak in 1971-72. Two had severe signs of poisoning and the other was clinically normal but had a high blood mercury concentration. Exchange transfusion resulted in clearance of mercury not only from blood but also from other tissues. The average amount of mercury removed in a two hour exchange was estimated as 6% of the body burden as compared to 1% of the body burden removed by normal excretion processes in 24 hours. No dramatic improvement in the clinical condition of the two poisoned patients occurred. Some improvement in motor power and function was observed during follow-up visits to their houses.