Great emphasis has been placed on recognition of the early warning symptoms of preterm labor by both pregnant women and health care providers. In addition to the expected increase in both painless and painful uterine contractions, several symptoms have been commonly cited in textbooks and patient educational materials as preceding preterm labor including menstrual-like cramps, backache, pelvic pressure, and an increased amount of vaginal discharge. We interviewed 107 women with preterm labor, 102 women with preterm prematurely ruptured membranes, and 106 ambulatory normal pregnant women to ascertain the frequency of each of eight putative warning symptoms of preterm labor in each group. Preterm labor patients were distinguished as expected from both normal women and amniorrhexis patients by a greater frequency of painful and painless contractions. Menstrual cramps, backache, and increased vaginal discharge, symptoms often said to be normally present in pregnancy, were also significantly more common in preterm labor patients than in women with preterm membrane rupture and in normal subjects.