The pathological anatomy, incidence, symptomatology, diagnosis and therapy of granulosa cell tumours are described using the example of a 5 1/2-year-old girl with this condition. The typical symptoms of pseudo-precocious puberty led to preoperative diagnosis of the granulosa cell tumour. These symptoms disappeared after left salpingo-oophorectomy; the girl is now developing normally. There have been no signs of metastases as yet.