Artificial abortions were performed in 7 midterm patients by inducing mechanical stimulation of the uterus by placement of laminaria tents in the cervical canal and a metreurynter into the lower uterine cavity to give a mechanical stretch. The changes of uterine contractility during the treatment were monitored by intraamniotic pressure recording. The intraamniotic pressure during the labor was usually within 50 mmHg, with a frequency of 2-5 times per 10 minutes; the resulting uterine activity (intensity X frequency) being 100-200. The fetus was aborted unharmed in all cases. The delivered placentas were histologically normal throughout their thickness (amnion, chorion, and decidua). Some theoretic considerations are given on the mechanism of onset of labor induced by mechanical uterine stretch.