A large stone with 8.7 cm multiply 7.2 cm multiply 6.5 cm in size and 420 g in weight dropped down spontaneously from a 93-year-old man's scrotum, who had suffered from left intrascrotal mass and pain for more than 20 years. The component of the stone was magnesium ammonium phosphate. To the best of our knowledge, it is the largest intrascrotal calculus reported in the world. We hereby present the case and discuss the diagnosis and etiology of scrotal calculi.