Posted 4/07 [M] I had a female friend in her twenties who was a medical assistant in a Doctor's office who told me about some of her experiences. She was usually present in the room during physicals and other exams that involve examining the penis, testicles and rectum. She usually but not always assisted a female doctor and she would typically just stand near the doctor during the exams taking down notes if the doctor instructed her to do so. She said that about a third of the men would get full erections. It would depend on which doctor she assisted as to how their genitals were exposed. Some would have them stand and pull up the gown and sometimes the gown would be pulled back by the doctor while the patient was lying on their back. To her surprise and embarrassment the penis would sometimes be erect. She said in some cases if the penis wasn't erect at first then after a minute or two it might become erect depending on the exam. If the penis was cultured at the opening with a Q-tip looking swab then it would exposed longer and more likely to become erect. However, the most likely cause of an erection is the prostate exam which is done by inserting a finger in the rectum. She said the penis would go from soft to hard very quickly.

Posted 7/06 [M 22]True story about a recent doctor visit and erection during the exam.....I recently was having a discharge during bowel movements and after urinating so I went to a health center at a local university. They made an appointment for me with the staff urologist. Little did I know the urologist was an attractive women not too far out of medical school. I was nervous enough , dreading the exam, but when a young woman walks in and introduces herself as the doctor my heart raced. And to add to it, the university requires a chaperone when doctors of the opposite sex must perform a genital exam so in walks a female nurse even younger than the doctor. 
They didn't waste any time. I had to strip and begin with an examination of my penis and testicles. Well with all the pulling and poking around I started to get aroused. The doctor said she needed to try and "express" the discharge so she squeezed and milked my penis. She did not get enough out so with the nurse watching she inserted a long q-tip into my pee-hole which burned like hell but wierdly made me harder than before. 
Just when I thought I could pull up my pants and hide my growing erection, the doctor said due to the nature of the discharge that she would have to check my prostate. She made me spread my legs wide and bend down over the table with the nurse having a prime view of my ass for the impending exam. Now i was very aroused but luckily I was facing the table so they couldn't get a full view, that would have been so embarrassing. I had never had a prostate exam so did not know what to expect but I thought I was gonna piss all over the floor. 
Then after the exam, my ass still greasy, she once again milked my penis for discharge. They were both kind enough to ignore my erection and luckily I made it out of the office without having an accidental ejaculation. that experience was embarrassing but really enjoyable at the same time. If I ever have prostatitis again I will request a female doctor from now on...plus they have smaller fingers.