Objective: To evaluate and to compare the predictive value of cervicovaginal beta-hCG and prolactin levels in spontaneous preterm delivery. Methods: The preterm labor group and normal pregnancy group consisted of 17 and 43 patients between 24 and 36 weeks' gestation, respectively. A single cervicovaginal beta-hCG and prolactin measurement were made in both groups. Results: Cervicovaginal beta-hCG and prolactin levels were significantly higher in the preterm group when compared with those of the term delivery group (P = 0.031, P = 0.026, respectively). The optimal cut-off value for beta-hCG (27.1 mIU/ml) gave a sensitivity level of 87.5% (47.4-97.9; 95% C.I.) at a specificity of 65.4% (50.9-78.0; 95% C.I.) with positive and negative predictive values of 28% and 97%, respectively. The optimal cut-off value for prolactin (1.8 ng/ml) gave a sensitivity level of 50% (16.0-84.0-, 95% C.I.) at a specificity of 96% (86.8-99.4; 95% C.I.) with positive and negative predictive values of 67%, and 93%, respectively. Conclusions: Cervicovaginal beta-hCG measurement in patients with preterm labor may be used as a predictive test. Cervicovaginal prolactin is not a sensitive test compared with the beta-hCG test. (C) 2001 International Federation of Gynecology and Obstetrics. All rights reserved.