INTRODUCTION Leydig cell hyperplasia (LCH) of the testis is rarely described in children. The authors report a case of incidental discovery of LCH on ultrasound examination. CASE REPORT The authors report the case of a 9-year-old boy presenting with isolated and painless increased volume of the left testis, with no clinically palpable mass. Scrotal ultrasound revealed an echogenic mass, 12 mm in diameter, with a solid appearance and several hypoechoic areas, without calcification, situated in the lower pole of the testis. Tumour markers and gonadotropin axis hormonal assessment were normal. On surgical exploration, the testis had a macroscopically normal appearance; opening of the tunica albuginea revealed the lesion and enucleation was performed. Histological examination confirmed the presence of LCH, 5 mm in diameter. The postoperative course was uneventful. Physical examination and scrotal ultrasound have remained normal with a follow-up of two years. DISCUSSION The authors recall the characteristics of LCH, which usually presents, in children, in the form of signs of precocious puberty or more rarely by gynaecomastia. The lesion is rarely palpable. Scrotal ultrasound reveals a homogeneous mass with several hypoechoic nodules. An endocrine assessment must always be performed (frequent elevation of LH). Surgery should be as conservative as possible (enucleation-resection). Histological diagnosis may be difficult.