Background: A huge number of inefficient embryo implantation caused by embryo transfer techniques. Cervical mucus aspiration is the most important factor in successful embryo transfer. Based on reports pregnancy rate in woman with positive culture of cervical mucus is lower than women with negative culture. Mucus plague on the catheter tip can cause improper embryo implantation. This study evaluated the effect of cervical mucus aspiration on embryo transfer results.Materials and Methods: A Randomized Clinical trial study was performed on 340 women (in two groups) by cycles of ART (Assisted reproductive technology) such as IVF (In vitro Fertilization) or ICSI (Intra cytoplasmic sperm injection) referred to the Research and Clinical Center of Infertility and Madar Hospital of Yazd. Male's and female's age, duration and cause of infertility were matched in two groups. The long time protocol was used for induction of the ovaries. In 170 patients, cervical mucus aspiration was done with insulin syringe (A or case group). In the control group or group B (170 women), cervical mucus was aspirated only with cotton swabe. The patients were followed up by ß-HCG serum level measurement on the day 14 after embryo transfer. The data were analyzed by Chi-square and t-test.Results: Mean of men's age in group A was 35.26±5.2 years and in group B was 35.13±5.4 years. Mean of women's age in group A was 29.8±5.3 years and in group B was 30.2±5.4 years. Mean of infertility duration was 8.6±4.6 years in both groups. Mean of follicle number, oocytes number, embryos number, cause of infertility and IVF/ICSI method in both groups were similar and there was no significant difference.Pregnancy rate in group A, was more than group B, (26.9% Vs 19.2%), but was not statistically significant.Conclusion: Cervical mucus aspiration with insulin syringe before embryo transfer can increase the pregnancy rate. This has confirmed by other studies, so it seems that cervical mucus aspiration before embryo transfer is useful.