Support during labor has been offered by a variety of different people, including fathers, professional medical staff, trained labor coaches and monitrices, untrained lay supporters and family and friends. A comparison of the various findings shows that support given by trained or lay untrained female supporters, who are not necessarily known to the laboring woman, yields the most extensive, methodologically sound, and consistently positive effects on obstetric and psychosocial outcomes. Although trained labor coaches have been shown to exert a positive effect on outcome, the results of doula support are the most impressive when both methodology and outcome effects are considered. Studies of father support have yielded contradictory findings, although women do appear to value their presence in most studies. Family and friends have not been shown to influence outcomes. Support from professional medical staff is rare, but when given, has, in some cases, had a positive effect. These findings are important for the field, since the use of lay supporters constitutes a low-cost preventive intervention. The inclusion of lay supportive women is also consistent with traditional practices in most countries in the world.