A fifteen year-old girl presented with several fractures after a road traffic accident. Five days later, fat embolism occurred, complicated by adult respiratory distress syndrome (ARDS) and disseminated coagulation (DIC). She was successfully managed in the intensive therapy unit, and was transferred to a general surgery after five weeks. Tachycardia and fever persisted without any other sign of infection. Clinical examination showed exophthalmos and a thyroid murmur. The venous concentration of T4 was increased: 204 nmol . 1(-1) (N: 70-150), whereas that of T3 was normal: 2.3 nmol . 1(-1) (N: 1-1.25). No other investigations were performed. The regression of clinical symptoms and a normalization of T4 were seen after treatment (carbimazole and acebutolol). Post-traumatic hyperthyroidism is discussed. Although classical, this syndrome was not well documented, as was shown in the literature survey. After trauma or an acute illness, an early fall in thyroid hormone concentrations was usually seen; a late increase in T4 was a rare occurrence.