Male Sprague Dawley rats have been contaminated with Ureaplasma urealyticum (by injection in their kidney of a 10(8) C.C.U. suspension of micro-organisms of human origin). They produce urinary tract stones similar to the humans ones and composed of struvite crystals (NH4MgPO4, 6H2O). It is concluded that such a model is a very good tool to develop new research on struvite lithiasis.