Isolated peripheral precocious puberty due to recurrent ovarian cysts evokes a McCune-Albright syndrome (MAS). This syndrome associates endocrine dysfunction such as precocious puberty, polyostotic fibrous dysplasia, and "café-au-lait" skin lesions. We report the case of a 3-y-old girl who presented with peripheral puberty with extremely elevated oestradiol level, low LH and FSH levels, and an ovarian cyst that quickly resolved. Skeletal X-rays were normal and she had no café-au-lait spots. GnRH analogue treatment was ineffective. A second ovarian cyst appeared and was completely drained under ultrasonographic guidance. Molecular biological analysis performed on fluid cells revealed the Arg201-->His mutation of the Gs alpha gene described in MAS. Percutaneous aspiration of simple ovarian cyst to detect "MAS" mutation is of interest in the diagnosis of recurrent ovarian cyst.