This study aimed at the influence of temperature on the vasoconstrictive effect of norepinephrine on rings of rat aorta and at the cause of the change observed. At the temperatures of 39.5 degrees C, 36.5 degrees C and 33.0 degrees C respectively, the vasoconstrictive force-time curve induced by norepinephrine and the equation of function were fitted. Statistical evaluation of the data was performed by F test. The difference was statistically significant (P < 0.01) among the three groups for relation constant X1 of function equation, but no significant difference (P > 0.05) was noted among the three groups for relation constant X2. Our experiments demonstrated that norepinephrine-induced vasoconstrictive force, in rat aorta, was obviously modulated by temperature. As the temperature of rat aorta was raised, the vasoconstrictive force and vasoconstrictive speed increased, and the effects of norepinephrine on vasculature were raised. The results suggest that the constant X1 for vasoconstrictive force is a factor sensitive to temperature.