A penis enlargement pump is a cylinder enlargement device fitted over the penis with a manual or motorized pump to create suction. Blood is drawn into the penis as the apparatus creates a vacuum around the penis, causing it to become engorged. The higher the vacuum, the higher the blood-pressure becomes within the penis; excessive pressure causes vascular damage rather than a harder penis.

Using a penis pump produces a lot of pressure which will slightly enlarge the penis temporarily. However, the gain is lost because the penis was only worked for a short period of time.

Penis pumps must be used very carefully to avoid injury; manufacturers' instructions should be followed. Manual pumps often recommend a gentle pump followed by a pause, then repeated. Over-enthusiastic pumping can burst blood vessels and form blisters. In some cases the testicles can be unexpectedly pulled into the cylinder and cause severe pain and injury. It is also believed that the rim of the cylinder can cut into the skin and over time cause damage to the ligaments surrounding the penis. These dangers can be avoided by following instructions.

Penis enlargement pump are also used for masturbation. In August 2006, Oklahoma district court judge was sentenced to four years in prison for repeatedly having masturbated with a penis pump while presiding over court cases.

Penis enlargement pumps, sometimes called vacuum pumps by the medical establishment, have been used to treat impotence. The pump is essentially as previously described, although often made to higher standards of quality with a much higher price, and distributed by suppliers of medical equipment.

As mentioned, it's very easy to injure yourself, especially if you have a cheap pump. Unless you have a pump that shows the pressure you're bound to try for more pressure because pumping doesn't really feel that much like it's doing anything most of the time. It's possible to bust a blood vessel which will necessitate some serious rest. For those seeking penis enlargement and enhancement, it is recommended that other, safer methods are used, and the Penis enlargement pump should be avoided.

The most recommended means of enlargement is simply manual exercises such as the jelq. These are more tedious but much safer and a far better choice in the long run.