Infertility & Sexual Dysfunction(구연) (E-189) Longer semen collection time is related to greater semen volume and total motile sperm count Urology, CHA Gangnam Medical Center, CHA University, Andrology lab, CHA Gangnam Medical Center, CHA University, Andrology lab, CHA Gangnam Medical Center, CHA University, Andrology lab, CHA Gangnam Medical Center, CHA University, Andrology lab, CHA Gangnam Medical Center, CHA University, Urology, CHA Fertility Center, Seoul Station, CHA University, Urology, CHA Gangnam Medical Center, CHA University Dong Suk Kim, Young Sun Her, Dong Hyuk Shin, Mihee Oh, Jeongwon Beak, Dae Keun Kim, Seung-Hun Song Background: Semen parameters may vary considerably from one specimen to the next, partly due to variability in the conditions under which the specimens are produced. The level of comfort in the semen collection room, adequate visual and auditory stimulation, and sufficient semen collection time may affect the quantity and quality of collected semen.  / Objectives: We evaluated the influence of semen collection time on quantity and quality of semen produced by masturbation. / Materials and Methods: A total of 250 men who delivered two semen samples for semen analysis with an interval of 2 weeks to 3 months at fertility center of CHA Gangnam Medical Center between Jul 2018 and Dec 2018 were included in the study. First semen collection was performed after standard brief instruction by an andrologist. Before second semen collection, more detailed instruction and emphasis on enough stimulation was explained by the andrologist. All subjects were requested for a 2 to 7day abstinence period before providing each semen sample. Semen analyses were performed according to the World Health Organization (WHO) 2010 guidelines. Men with azoospermia or cryptozoospermia were excluded. Semen collection time was regarded as the time between entering the semen collection room and submitting a semen sample. We investigated the difference in the semen collection time, semen volume and quality including sperm concentration, motility and strict normal morphology of the two semen samples. / Results and Conclusion: Semen collection time was significantly longer in second semen collection, which was performed after more detailed instruction and emphasis on enough stimulation. Semen volume and total motile sperm count were significantly higher in second semen collection. However, sperm concentration, sperm morphology, and strict normal morphology showed no differences between the two semen samples. More detailed instruction and explanation of importance on enough stimulation during semen collection is related to longer semen collection time, larger semen volume and more total motile sperm count. This study was performed in subfertile population, but it could be applied for cancer patients who want sperm banking just before start of chemotherapy.     keywords : semen collection time, semen analysis