Ureaplasma urealyticum is a fastidious organism which is not recovered by conventional bacterial cultures techniques, but special cultures are required for its isolation and identification. As it is a urease-producing organism, it is considered a risk factor for the formation of struvite calculi in the urinary tract. A total of 30 patients with urinary infection stones (19 of them with the 1st formation and 11 with recurrent stone formation) were included in the study. Both bladder urine specimen (cystoscopically obtained) and stones removed were subjected to conventional cultures and also to Ureaplasma specific cultures (A7 agar and U9 broth). The results of culture techniques revealed that 86.7% of patients had aerobic organisms (E. coli in 46.7%, Klebsiella in 30%, Proteus in 6.7% and Pseudomonas in 3.3%) and 26.7% showed U. urealyticum in mid stream urine. As regards stone cultures, they revealed aerobic organisms in 76.7%, and U. urealyticum in 20%. Sensitivity tests for U. urealyticum showed that minocycline was the most effective antimicrobial followed by tetracycline and ciprofloxacin. From these data, we conclude that U. urealyticum may be the causative organism for infection stone and should be searched for via its specific cultures, especially in patients with recurrent stones and with the so-called sterile pyuria.