Thirty euthyroid patients hospitalized for completed stroke had serum thyroxine, triiodothyronine, thyroxine-binding globulin and thyroxine-binding prealbumin levels significantly decreased (p less than 0.01 to p less than 0.001) compared with 70 age- and sex-matched healthy controls. Admission serum thyroxine levels gave the best correlation with mortality (T4 less than 65 nmol/l = 100% mortality; 65-77 nmol/l = 38%; 78-90 nmol/l = 9%; greater than 90 nmol/l = 0%). In general, during hospitalization a progressive decrease in serum concentrations of these parameters was observed in the 11 patients who subsequently died, while there was a progressive increase in the 19 survivors. However, the most sensitive index of clinical recovery appeared to be prealbumin, since a decrease in prealbumin levels was observed in all subjects who died, and an increase in prealbumin was found in all survivors.