Intravenous injections of histamine (20-600 micrograms) as well as of compound 48/80 (10-100 micrograms), a histamine releaser, produced a significant drop in the cloacal temperature of pigeons when examined during the initial 2 hr period following the injections. The effect of histamine was dose-dependent. A trend towards a drop in foot temperature was indicated with higher doses of histamine, but no effect was seen with compound 48/80. Plasma free fatty acid (FFA) levels were significantly increased at 15 and 30 min post-injection of histamine but an increase with compound 48/80 was obtained only at 15 min. While histamine produced a hyperglycaemic effect that was significant only at 30 min post-injection, compound 48/80 showed no such effect. Histamine caused a significant drop in the plasma levels of thyroxine (T4) and triiodothyronine (T3) both at 15 and 30 min post-injection. A similar trend in the thyroid hormone levels was also produced by compound 48/80, except for the T4 level at 15 min post-injection which showed no change.