Originally uploaded by varf

 A beef tenderloin, known as an eye fillet in New Zealand and Australia, filet in France and fillet in England, is cut from the loin of beef.

As with all quadrupeds, the tenderloin refers to the psoas major muscle anterior to the transverse processes of the lumbar vertebrae, near the kidneys. This muscle does very little work, so it is the most tender part of the beef. The tenderloin can either be cut for roasts or for steaks.

Tenderloins from steers and heifers are most common at retail, but those from cows are common in foodservice applications, such as less expensive steakhouses.

A common misconception is that the tenderloin is also called a Chateaubriand steak, when in fact, the Chateaubriand is a recipe for a particular tenderloin steak which originates from France.

Typically, the Chateaubriand is taken from the center-cut of the tenderloin, in a large enough portion to feed two. There are three main "parts" of the tenderloin: the butt, the center-cut, and the tail. The butt end is usually suitable for carpaccio, as the eye can be quite large; cutting a weight-portioned steak from the butt will invariably yield a very thin steak. The center-cut is suitable for portion-controlled steaks as the diameter of the eye remains relatively consistent. The center-cut can yield the traditional 'fillet mignon' or tenderloin steak, as well as the Chateaubriand and Beef Wellington. The tenderloin tapers off into a tail, which is generally unsuitable for steaks due to consistency of size concerns, but can be used in recipes where small pieces of a tender cut is called for, such as Stroganoff.