Erectile dysfunction is the inability to achieve or maintain an erection sufficient for satisfactory sexual performance.  While more common among older men it can affect men of all ages.  Most common causes for ED are atherosclerosis (poor blood flow), Diabetes (affects nerves and vessels), low testosterone levels, neurologic conditions (Parkinson's, MS), certain medications, psychological factors (stress, anxiety, depression), poor lifestyle habits (smoking, excessive alcohol, sedentary lifestyle).  Symptoms include difficulty achieving or maintaining an erection, reduced sexual desire, and anxiety/stress related to sexual performance.  If you suffer from ED it is important to discuss the issue with your doctor who can order your testosterone level and identify and correct the underlying causes. Other than correction the underlying factors, treatment for ED aims to improve testosterone levels (if low) or improving blood flow with PDE 5 inhibitors such as Sildenafil (Viagra), Tadalafil (Cialis) and Vardenafil (Levitra).  In more severe and refractory cases a Urology consultation maybe necessary.