In two previous communications the author reported the results of pharmacological studies on the nonpregnant human uterus. The present paper deals with the results of comparative studies on the automatism and pharmacological reactions between pregnant and nonpregnant uterus, such as have never been tried by any investigator. The follo wing conclusions have been reached. I. The strip of a pregnant human uterus produces more vigorous automatism, by means of Magnus' method, than that of nonpregnant uterus. II. Automatism in the human uterus, and its sensibility to autonomic poisons, uterine stimulants and other drups, are the same regardless of the state of pregnancy, whether early or late, or normal or ectopic. III. A pregnant uterus reacts to the drugs more vigorously than a nonpregnant one. The difference in the effect of the drugs on a pregnant and a nonpregnant uterus is quantitative with certain kinds of drugs, while a qualitative difference is shown with some other drugs. Adrenalin, pilocarpin, acetylcholin, pituitrin and nicotin belong to the former group, while bombelon, secacornin and caffein are included in the latter. Atropin shows no difference in its action on the uterus whether it is pregnant or nonpregnant. 1. Adrenalin and pituitrin show a stronger stimulative effect on a pregnant uterus than on a nonpregnant one. The effect of caffein on a pregnant uterus is stimulative, while it acts as the depressant on a nonpregnant uterus. Therefore it may be said that the excitability of the motor-sympathetic is increased during pregnancy. 2. The stimulative actions of pilocarpin and acetylcholin are more evident in a pregnant uterus than in a nonpregnant one. So the excitability of the parasympathetic nerve is also accelerated during pregnancy. 3. Nicotin exerts a more actively depressive effect on a pregnant uterus than on a nonpregnant uterus. From this fact it may be learned that the excitability of the sympathetic nerve is increased, not only in the motor fibres but also in the depressor. 4. Bombelon and secacornin produce a stimulative effect on a pregnant uterus owing to the stimulation of the muscle. Such action from these drugs is not seen in a nonpregnant uterus. This fact shows us that the excitability of the uterine muscle is heightened during pregnancy and that this increased excitability is greater in the uterin muscle than that shown in the sympathetic and parasympathetic nerves.