The size of the prostate gland can change as men age, and an enlarged prostate can cause problems with urination. The average adult prostate is about the size of a walnut, weighing between 20 to 25 grams. By the age of 40 years, the prostate may be as large as an apricot, and by the age of 60 years, it may be the size of a tennis ball, lemon, or larger. However, size is not the only factor used to determine whether an enlarged prostate is dangerous. When doctors evaluate the prostate, symptoms are just as important as size. In addition, size and symptoms dont always correspond. For example, one person might have a mildly enlarged prostate with noticeable symptoms, while another person could have a very large prostate with no symptoms. An enlarged prostate becomes dangerous when it prevents the proper flow of urine, potentially causing backflow that leads to bladder and kidney infections. In some cases, an enlarged prostate can block urine flow completely or result in kidney failure. Therefore, it is important to consult a doctor if you experience any symptoms related to urination or if you have concerns about the size of your prostate.