The present disclosure is directed to a method of treating overactive bladder comprising orally administering to a subject in need thereof an amount of from about 60 mg to about 90 mg (e.g., about 75 mg) of vibegron per day. The present disclosure is also directed to a pharmaceutical unit dosage composition comprising from about 60 mg to about 90 mg (e.g., about 75 mg) of vibegron for oral administration.