Plasma concentrations of desoxycorticosterone (DOC) and aldosterone are markedly elevated in pregnancy. Although DOC secretion in nongravid women has been assumed to be dependent mainly on adrenocorticotropic hormone (ACTH), in a previous study of women in the third trimester of pregnancy it was found to be unresponsive to ACTH, dexamethasone, and variations in salt intake. In this study plasma DOC, aldosterone, and cortisol levels, as well as their responses to ACTH stimulation and overnight dexamethasone suppression, were observed sequentially in seven normal women during the course of pregnancy and at three months post partum. Plasma DOC, aldosterone, and cortisol levels rose substantially during gestation, but increments in DOC did not necessarily coincide with those of the other two. Responses of all three corticosteroids to ACTH were enhanced during the first two trimesters compared to the nongravid state; DOC became unresponsive in the third trimester, while aldosterone and cortisol rose to an even greater extent. Elevated maternal DOC was not decreased significantly by dexamethasone at any stage of pregnancy, while plasma cortisol was suppressed. Nonsuppressibility of DOC with dexamethasone and also the lack of correlation of the rise in DOC with the increase in cortisol during the course of pregnancy suggest that increased DOC secretion in pregnancy does not arise from ACTH-dependent pathways of the maternal adrenal. The loss of responsiveness of DOC to ACTH in the third trimester suggests that the maternal adrenals have undergone an alteration in their steroidogenic response to ACTH, but also may indicate that their output of DOC has reached a maximal rate. © 1978.