Abstract: Despite recent advances in perinatal care, Preterm Premature Rupture of Membranes (PPROM) continues to lead to important obstetric complications. This study was aimed to evaluate the role of sonographic measurement of myometrial thickness in prediction of latency interval in women with PPROM. This analytic- descriptive and case- control study was performed on pregnant women with PPROM presenting to Tabriz Al-Zahra Hospital since 2006 to 2008. Thirty pregnant women with PPROM and 30 pregnant women with normal pregnancy were enrolled. Mean gestational age was 30.60±1.99 week and in case and 31.13±20.01 week in control group (p = 0.307). Mean gravidity was 1.63±0.49 in case and 1.47±0.50 in control group (p = 0.210). Mean parity was 0.53±0.62 in case and 0.57 0.50 in control group (p = 0.819). Mean anterior myometrial thickness was 8.23±2.59 mm in case and 7.71±1.45 mm in control group (p = 0.344). Mean posterior myometrial thickness was 8.90±2.86 mm in case and 8.12±1.54 mm in control group (p = 0.197). Mean fundus myometrial thickness was 9.10±3.54 mm in case and 8.77±1.77 mm in control group (p = 0.648). Mean latency interval of women with PPROM was 18.70±20.68 day and mean sonography to labor interval was 57.30±16.14 day (p<0.01). Mean latency interval of women with PPROM was significantly shorter than mean sonography to labor interval in control group patients (p<0.05). In our study, 50% of women in 10 first days after PPRM labored and only 43.3% of women labored in 7 first days after PPROM. In this study, significant correlation was not found between myocardial sickness in anterior, posterior and fundus with latency interval.