Urinary cyclic AMP and cyclic GMP excretions were measured in 24-h urine specimens obtained from 89 women at various times during their normal uncomplicated intrauterine pregnancies and from 49 women at various times after the births of their normal healthy infants. Cyclic AMP excretion increased steadily from the beginning of the second trimester or earlier until late in the third trimester, reaching a peak excretion approximately 40% greater than that of normal nonpregnant women. The cyclic AMP excretion dropped abruptly by the first day after parturition to levels which were not significant different from those of normal non-pregnant women. In contrast, cyclic GMP excretion increased rapidly during the first trimester and remained relatively constant during the remainder of the pregnancy, reaching a peak excretion of about 140% greater than that of normal nonpregnant women. Furthermore, it decreased slowly toward normal levels, but was still significantly elevated six weeks after parturition. The factors responsible for the increased excretion of cyclic AMP during pregnancy and for the increased cyclic GMP during and after pregnancy are not known.