OBJECTIVE: To determine the effect of luteinized unruptured follicle (LUF) cycles on frozen thawed embryo transfer (FET). DESIGN: A retrospective analysis comparing the clinical outcomes after FET among 144 cases of luteinized unruptured follicle (LUF) cycles and 866 cases of ovulation cycles. SETTING: Reproductive medical center, Beijing China. PATIENTS: Chinese infertile women who underwent FET. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Clinical pregnancy rate (PR), implantation rate. RESULTS: The implantation rate, clinical pregnancy rate, on-going pregnancy rate and live birth rate in LUF group were 12.76% (49/384), 27.78% (40/144), 24.31% (35/144) and 19.44% (28/144), respectively, and in ovulation group, 14.74% (332/2251), 31.29% (271/866), 28.29% (245/866) and 22.23% (193/866), respectively (p > 0.05). CONCLUSIONS: LUF does not affect the clinical outcomes of FET. Patients of LUF should be included in FET treatment.