While controversy exists as to the relationship between maternal position in labor and such measures as the labor duration, subjective discomfort, and fetal outcome, little appears to be known about the positions women assume in labor when they are permitted to do so without coercion or instruction. To learn more about maternal position in labor, we observed 80 consecutive patients with uncomplicated normal spontaneous vaginal delivery over the course of labor to ascertain the positions volitionally chosen by each. Data were collected on position preferences and phase of labor. All labors were analyzed; a codified lexicon was established to describe the position pattern in each phase and the principal positions the patient assumed over the course of labor. The frequencies and distributions were determined for nulliparas and multiparas separately and rates of position change were assessed. It was found that gravidas chose a number of different principal positions in the early phases of labor, but that they became more narrowly selective in the deceleration phase and second stage; at the same time, they tended to change position more often in late labor.