Six hundred and forty Glasgow children, initially aged between 11 and 14 years, were interviewed twice, with approximately one year between interviews. Children whose intentions to smoke when older became more positive between the two interviews tended to be more aware of cigarette advertising at the time of the first interview (compared with children whose intentions to smoke were negative at both interviews). Children whose intentions to smoke became more negative between the interviews tended to be less appreciative of cigarette advertisements at the time of the first interview (compared with children whose intentions to smoke were positive at both interviews). Since both groups differed from their respective contrast groups before their declared intentions changed, these findings support the view that cigarette advertising has predisposing as well as reinforcing effects on children's attitudes and behaviour with respect to smoking.