Condoms are thin sheaths worn by men during sexual intercourse to prevent pregnancy and venereal infections. According to the 1995 National Survey of Family Growth, conducted by the National Center for Health Statistics in Hyattsville, Maryland, male condoms or prophylactics are the third most popular form of birth control—preceded only by female sterilization (29.5%) and birth control pills (28.5%)—with usage at 17.7%. They are also one of the most effective: research indicates that with correct use, failure rates are 2-3%. Most condoms are made of latex rubber, but they can also be made from lamb cecum or polyurethane. In addition to their contraceptive value, condom use has been found effective in preventing the spread of sexually transmitted diseases. In 1986, the U.S. Surgeon General endorsed the use of condoms as the only currently available effective barrier against the transmission of Acquired Immunodeficiency Syndrome (AIDS). The spread of many other sexually transmitted diseases, such as chlamydia and gonorrhea, can also be virtually eliminated with the use of a latex condom. With the government touting the health benefits of condom use, manufacturers openly advertise their products, and retailers stock condoms in visible, accessible locations. Condoms, previously kept behind the prescription counter, are now found on most store shelves. Today in the U.S., 450 million condoms are sold each year. Despite the wide variety of styles, there are few differences among the many latex condoms available on the market today. They can be straight-sided, contoured, ribbed, sensitive, or smooth. They may be treated with lubricants or spermicides. They can be blunt-ended or have a reservoir tip. Because the condoms undergo stringent testing before they are sold, quality is generally not a marketable issue. Hence, manufacturers attempt to build brand loyalty and market their products to specific target consumers. Condoms made from lamb cecums—the blind pouch in which the intestines begin and into which the ileum opens from one side—are also available. However, they are more expensive than latex condoms, and while they prevent pregnancy, “skin” condoms are ineffective in preventing the transmission of sexually transmitted diseases. In 1994, the Food and Drug Administration (FDA) approved a polyurethane condom for sale in the U.S. The new condom has not been extensively tested for effectiveness in preventing pregnancy and sexually transmitted diseases.