Abstract: One hundred SD male rats were randomly divided into 3 groups： group A, 45 rats, ureaplasma urealyticum (u. u. ) were inoculated into the bladders； group B, 22 rats, in addition to the inoculation of u. u., minomycin(20-100 mg/kg.day) was administrated for 14 days 3 months after the inoculation； group C, 33 rats as the control. The results showed that (1) the u. u. infective rates were 87.5%, 20% and 0% for group A, B and C respectively (P＜0,001, group A versus group B)； (2) the incidences of bladder calculus were 40%, 35% and 0% for group A, C respectively (P＞0.1, group A versus B). The possible relationship between bladder calculus and u. u. infection was discussed.