AIM: To assess the relationship between ureaplasma urealyticum (UU) infection, vertical transmission pathway and diseases in neonates.METHODS: Specimens of amniotic fluid and cervical swabs from 30 women at delivery, and nasopharynx and urinary mouth secretions from 161 neonates were cultured for UU. RESULTS: The UU positive rate of 30 women at delivery and 8 neonates from puerperas with UU infection were 26.67% and 62.7%, respectively. The detective rate of UU in normal neonates (26 of 130, 20%) was significantly lower than that in sick neonates (14 of 31, 46%) ( P