Objective: To compare the reproductive outcomes of frozen-thawed embryo transfer (FET) in nature cycle utilizing monitoring ovulation regimen (MOR) and monitoring progesterone (P) level regimen (MPR). Study design: A retrospective analysis of records of 224 women who received FET procedures. Result(s): MPR was used in 60.3% (135/224) of cycles and MOR in 39.7% (89/224) of cycles. The clinical pregnancy rate per transfer was 63.0% in the MPR group and 48.3% in the MOR group (p = 0.030). The implantation rates were 42.6% and 35.1%, respectively (p = 0.001). The ongoing pregnancy rates per transfer (at 12 weeks' gestation) were 54.1% and 41.6%, respectively (p > 0.05). A logistic regression analysis showed that the type of natural cycle regimen was a predictor of clinical pregnancy rate (odds ratio, 1.996; 95% confidence interval, 1.123-3.549; p = 0.019). Other significant variables affecting clinical pregnancy rate was number of top-quality embryos transferred. Conclusion(s): Performing FET using MPR could achieve higher clinical pregnancy rate compared with MOR in a group of patients with the comparable demographic and cycle characteristics profile. (C) 2014 Elsevier Ireland Ltd. All rights reserved.