Aim: To determine the optimum time for endometrial scratching in patients with unexplained primary infertility undergoing ICSI-ET cycles after one or more implantation failure. Methods: A randomized clinical trial wasconducted at fertility care unit, Mansoura University Hospital and 2 private fertility centers, Egypt, fromNovember 2016 tillJune 2018. Eligible participants [142] had unexplained primary infertility, were prepared and sched- uled to obligate for ICSIcycles. Patients were randomly allocated into two equal groups using computer-generated tables and sealed opaque envelopes. Endometrial scratching was done either just af- ter oocyte retrieval in (group 1) or mid-luteal in the cycle before induction (group 2). Patients, investigators, and data analysts were not masked to group assignment. The primary outcome measure was implantation rate while the clinical pregnancy rate was settled as the secondary outcome measure. Results: one hundred forty two clients were included (71 in each group). Baseline characteristics did not differ between both groups as regard the age, BMI, duration of infertility and basic laboratory inves- tigations (p>0.05). The mean estimated day of triggering (14.2 ± 2.1 in G1 vs 13.6 ± 2.2 in G2) together with the mean follicular size (19.3 ± 0.8 in G1 vs 18.5 ± 1.8 in G2) showed also no statistical significance (p values 0.690 and 0.751 respectively). Again, the mean estimated number of ova retrieved (7.4+ 2.1 in G1 vs 7.1+ 1.3 in G2) and zy- gote transferred (2 in each group) presented no significant differences together with the chemical pregnancy rates (54 in G1 vs 52 in G2, p>0.05). On the other hand, IR and CPR are found significantly high- er in group 1 compared to group 2, (IR 53.5% vs, 40.8%; whilst CPR 49.3% vs 35.2%, p<0.05). Conclusion: retrieval day endometrial scratching seemed to improve clinical pregnancy and implantation rates than does mid-luteal endo- metrial scratching in patients with unexplained infertility