To date, the focus of sex education research has tended to be on the effect of education on behavioral outcomes. There is little data on the felt needs of young people, how well they are met, and how provision might be improved. Here we report on main source of information about sexual matters, adequacy of knowledge, further needs, and preferred source of additional information, using data from a probability sample survey of people aged 16 to 44 years in Britain (Natsal 2000). A total of 11,161 participants (4,762 men and 6,399 women) were interviewed. The response rate was 65.4%. The results show that despite the assumed worldliness and sophistication of young people about sexual matters, there is a great deal of self-perceived ignorance among them. Parents and schools are the preferred source of further information. We need to enable parents to provide information to their children, especially their sons. (Contains 3 tables.)