PURPOSE: Although suprapubic bladder aspiration (SBA) is relatively invasive procedure, it minimizes the risk of contamination through bypassing the normally colonized distal urethra. This study was performed to assess predicted average voiding time and to assess the success rate and efficacy of SBA in neonate. METHODS: We prospectively investigated 50 normal newborns to assess predicted voiding time, and 50 patients to access the success rate and efficacy of SBA. With 50 normal newborns, we examined diapers if they were wet after feeding, and repeated every 10 minutes. The voiding time had been decided at the time when the diaper had found to be wet. With 50 patients who need urine culture, SBA had been conducted at 25 minutes in dry group, and at 30 minutes in wet group. This time point of SBA was determined by one standard deviation close to the point of feeding time from predicted average voiding time in normal newborns. RESULTS: The predicted voiding time was 32 minutes (32+/-8minutes) in dry group, 40 minutes (40+/-6 minutes) in wet group (P<0.05). The success rate of SBA was 80% in dry group, 90% in wet group (P=0.34). CONCLUSION: SBA was more likely to be successful when performed at 25 minutes after feeding when the diaper was dry, and at 30 minutes after feeding when the diaper was wet.