This is a report on three cases of acute haemolytic disease in glucose-6-phosphate dehydrogenase (G6PD) deficient workers exposed to trinitroluene (TNT). The courses of the haemolytic crises have several features in common, the most striking being the onset of the disease within two to four days after the start of exposure, and the fact that this has been the first and so far the only haemolytic episode in their lives in spite of detailed medical records of past diseases, injuries, and medications during 12 to 16 years preceding the haemolytic crisis and five to nine years following the disease. The lowest haemoglobin levels for the three patients were 4-0, 6-8, and 8-2 g/dl respectively; haematocrit values were 17 and 24%; reticulocytes rose in case 1 to 26-2%, in case 2 to 26%, and in case 3 to 10%. Indirect bilirubinaemia was increased in two patients (5-1 and 2-6 mg/100 ml) and stercobilinogen was as high as 2150 mg/24 hr in one patient. The presence of the metabolite monoamino 2-6 dinitrotoluene was proved in the urine of case 3 and reached 21 gamma%. The possibility of a dose-response relationship is briefly discussed and the risk of exposing G6 PD individuals in chemical processes is mentioned.