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Urology/Rock Hard Erection


Dear Mr. Leslie,
I have a very simple question for you. I am often hearing about erections being "rock hard." Exactly what does this mean?

I can't remember my erections ever being literally as hard as a rock, or a metal tube, etc. To the best of my knowledge, there is soft tissue surrounding the cavernous bodies which would make this physically impossible, correct?

I have psychogenic ED, and when I went to get a penile ultrasound, after being injected with the prostaglandin, I had a full erection. Normal inflow, 0 outflow. The technician said it was "hard as a rock." However, touching it, I knew it was not literally this hard. I could still even bend it very slightly, and then it would bounce back up. Same thing happens when I take viagra. Fully erect, no problems, but not LITERALLY as hard as a metal tube.

Isn't the "rock hard" thing an exaggeration? How hard does an erection need to be in order to confirm that one does not have ED?



"Hard as a rock" is an expression and not a medical term.  If you are getting a full and rigid erection, it is not required that it is literally as "hard as a rock".

Technically, an erection only needs to be hard enough for penetration.  If it can't get that hard, that would be ED.  From your description, you don't have ED.


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Stephen W. Leslie, MD


Questions concerning erectile dysfunction, kidney stones and prostate disorders including prostate cancer. I have a special interest in kidney stone disease prevention.


Full time practicing urologist with 30 years experience. Associate Professor of Surgery and Chief of Urology at Creighton University Medical Center. Editor in Chief of eMedicine Urology internet textbook. Author of only NIH approved book written for patients by a urologist on the subject of kidney stones "The Kidney Stones Handbook". Inventor of the "Parachute" and "Escape" kidney stone baskets and the "Calculus" stone prevention analysis computer program.

American Urological Association, Ohio State Medical Association, Sexual Medicine Society

Men's Health, Journal of Urology, Urology, Healthwatch Magazine, Emergency Medicine Monthly, eMedicine, "The Kidney Stones Handbook", and numerous articles in various newspapers. He is also the editor of the Urology Board Review by McGraw-Hill used by urologists to study for their Board Certification Examinations.

Graduate of New York Medical College with residencies completed at Metropolitan Hospital New York, Albany Medical Center and University of Wisconsin-Madison.

Awards and Honors
Thirlby Award of the American Urological Association. Rated as one the country's Best Urologists by the Independent Consumer's Research Institute

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