The variable designs and results of controlled trials of maternal position in labor are summarized. Following Mendez-Bauer 's design, the effects of sitting alternated with side-lying and supine alternated with side-lying were compared in terms of contraction intensity and frequency, uterine activity and efficiency, and maternal comfort. The effects of each position were influenced by the position it was alternated with and the phase of labor during which it was used. While contractions were more frequent when sitting, uterine activity and efficiency were greater while side-lying, both in early and late labor. There was no statistically significant difference in uterine activity or efficiency in the side lying position when compared to the supine (propped) position although contractions were more intense and less frequent while sidelying. These results suggest that position change is important in achieving efficient uterine contractions. (BIRTH 10:4, Winter 1983)