Fifty-eight primigravidas and 67 multiparas who entered the active phase of labor with intact membranes were randomly assigned to either a control or an amniotomy group. Length of the latent phase, active phase, total first stage, second stage and active phase plus second stage, as well as a number of nonlabor parameters were studied.For primigravidas the mean active phase, second stage and active phase plus second stage for the amniotomy group were shorter than the control's by 40 minutes, 26 minutes and 60 minutes respectively. For multiparas, only the mean active phase for the amniotomy group was shorter than the control's and by only 1 minute. There were no significant differences between the amniotomy and control groups with respect to the nonlabor parameters.