OBJECTIVE To investigate accuracy of fetal fibronectin testing to predict preterm birth in twin gestations with symptoms of preterm labor. METHODS We reviewed charts of all patients with twin gestations who underwent fetal fibronectin testing and presented with complaints of preterm labor between January 1, 2000, and June 30, 2004. We also reviewed the charts of all singleton gestations with similar complaints that had fetal fibronectin testing between January 1, 2000, and December 31, 2001. All samples were processed using a rapid fetal fibronectin detection system. We calculated the sensitivity, specificity, positive predictive value, and negative predictive value of fetal fibronectin testing in singleton and twin gestations in predicting delivery within 14 days of testing. RESULTS Four hundred twenty-nine singletons and 87 twins met the inclusion criteria. The birth rate before 34 weeks of gestation for singletons was 3.5% compared with the rate of twin pregnancies of 28.7%. Fetal fibronectin predicted delivery within 14 days of testing with a sensitivity, specificity, and positive and negative predictive values in singleton gestations of 82%, 90%, 17%, and 99%, respectively. In twin gestations, fetal fibronectin predicted delivery within 14 days of testing with a sensitivity, specificity, and positive and negative predictive values of 71%, 74%, 19%, and 97%, respectively. CONCLUSIONS As noted in singleton pregnancies, fetal fibronectin testing in twins has a high negative predictive value. Fetal fibronectin evaluation may be a useful tool in screening twins with symptoms of preterm labor, because a negative result places these women at a low risk for delivering within 2 weeks of testing.