As many as 1% of the population claim to be asexual--they claim that they do not experience sexual attraction. They are "indifferent to and uninterested in having sex with either gender." According to this article, some academic researchers have been trying to determine whether asexuality is a biological phenomenon or "a slippery social label that some people may prefer to adopt and embrace." It turns out, the topic is fraught with definitional issues. For instance, there are allegedly many ways of not being sexual:

[T]here is tremendous variation in the sexual inclinations of those who consider themselves to be asexual. Some masturbate, some don't. Some are interested in nonsexual, romantic relationships (including cuddling and kissing but no genital contact), while others aren't. Some consider themselves to be "hetero-asexual" (having a nonsexual aesthetic or romantic preference for those of the opposite sex), while others see themselves as "homo-" or "bi-asexuals." Yet many asexuals are also perfectly willing to have sex if it satisfies their sexual partners; it's not awkward or painful for them but rather, like making toast or emptying the trash, they just don't personally derive pleasure from the act. Others insist on being in completely sexless relationships, possibly with other asexuals.

AVEN (Asexual Visibility and Education Network) provides additional information regarding asexuals. In fact, I am related through marriage to the founder of AVEN (David Jay), a thoughtful young man who is absolutely sincere about his views on asexuality. I do struggle with the claim that one can be an asexual when one has lots of sex. On the other hand, I do know several adults who I suspect are asexual--I doubt that they have any sexual cravings. One of them is a woman with a chronically flat affect. The other is a man who had a horrific marriage, several decades ago, which apparently turned off his sense of sexuality permanently. Though it is my suspicion that virtually all healthy adults experience sexual feelings, I also suspect that there are some bona fide asexuals. I would like to see more science that might enlighten us as to whether this rather quiet segment of society is asexual due to nature, environment, choice, or something else.