Objective: Children's letters to Father Christmas provide an opportunity to use naturalistic methods to investigate the influence of television advertising. Methods: This study investigates the number of toy requests in the letters of children aged between 6 and 8 (n 98) in relation to their television viewing and the frequency of product advertisements prior to Christmas. Seventy-six hours of children's television were sam- pled, containing over 2,500 advertisements for toys. Results: Children's viewing frequency, and a preference for viewing commercial channels, were both related to their requests for advertised goods. Gender effects were also found, with girls requesting more advertised products than boys. Conclusion: Exploring the children's explicit understanding of advertising showed that children in this age group are not wholly aware of the advertisers' intent and that, together with their good recall of advertising, this may account for their vulnera- bility to its persuasive messages. (J Dev Behav Pediatr 28:1-1, 2007) Index terms: children, advertising, television, Christmas. With children in the UK watching an average of 2½ hours of television per day, 63% possessing a television in their bedroom 1 and the growth of commercial TV chan- nels in the UK, the potential exposure to television ad- vertising for today's children is considerable. There is now a growing body of literature examining the effects of television advertising on children, their understanding of it and the extent of its influence. This research is highly relevant to those concerned with the regulation of advertis- ing to children and those who see a need to protect children from aggressive marketing. 2 Young children are a vulnerable group, it is suggested, because they lack the cognitive skills necessary to defend themselves against the persuasive power of advertising. 3 This paper takes account of theories about children's development in assessing this vulnerability and uses a methodology that examines children's behavioral responses to television advertising. Advertisers are not completely free to bombard chil- dren with television advertising as regulations control the amount and type of television advertising targeted at children in many parts of Europe and the US. Neverthe- less, controls vary considerably from country to country ranging from few restrictions to timing restrictions to total bans on any TV advertising which is aimed directly at children. 4 In the UK the content and amount of adver- tising are regulated. 5 Nonetheless, while strict regulations