Unplanned pregnancy is a major public health problem in the United States. Although the U.S. Air Force has the highest proportion of active duty women of any of the U.S. military services, there are no published data on the occurrence of unplanned pregnancy among active duty Air Force (ADAF) women. Civilian female interviewers conducted telephone interviews with a random sample of 2,348 ADAF women during early 2002, using questions that were closely based on the 1995 National Survey of Family Growth. During 2001, approximately 12% of ADAF women had one or more pregnancies. By National Survey of Family Growth criteria, approximately 54% of these pregnancies were unplanned. Thus, approximately 7% of ADAF women had one or more unplanned pregnancies during 2001. Roughly one-half of unplanned pregnancies represented contraceptive nonuse and the other half represented contraceptive failure or misuse. Unplanned pregnancy is a serious and frequently occurring problem among ADAF women, with many opportunities for prevention.