To determine the usefulness of thyroid hormones measurement in predicting the prognosis of patients with severe multiple injuries, a total of 55 patients with severe multiple injuries (34 males and 21 females, with a mean age of 50.7 years) were evaluated between September 1996 and February 1999. The patients were evaluated within 2 hours of admission, and the serum free thyroxin (FT_4), thyroxin (T_4), free triiodothyronine (FT_3), triiodothyronine (T_3), thyroxin-binding globulin (TBG), injury severity score (ISS), and the acute physiology and chronic health evaluation (APACHE II) score were determined. The same tests were repeated with the exception of the APACHE II on day 1, day 3 and day 7. A comparison was made of these variables between the survivors (37 patients) and non-survivors (18 patients). The mean ISS was 35.1±15.3 and the mean APACHE II score was 17.7±12.0. The best predictors of the prognosis in a descending order were T_4 (p<0.0001), T3 (p<0.0001), FT_4 (p<0.0001), ISS (p<0.01), and APACHE II score (p<0.01). Measuring the thyroid hormones (T_4, T_3 and FT_4) within 2 hours of admission together with ISS and APACHE II score appear to be useful in predicting the prognosis of patients with severe multiple injuries.