Powerful Mass media effects have rarely been documented.1 This failure to find effects partly reflects the fact that effects are usually sought by studying levels of exposure to various media, whereas the major effects of mass media are associated with the presence or absence of the media themselves.2,3 Even when considering media effects of a narrower or less universal scope than those set forth by McLuhan,2 many of the more significant findings are based on studies of the introduction of a medium. For instance, a primary source of evidence that exposure to television may be a cause of violence is based on studies linking the introduction of television sets in different countries to subsequent increases in crime and, in particular, to increased homicide rates. In 1955, the year that television was introduced in Finland, television sets per capita ranged from 0.00 sets per capita in Finland to 0.22 television sets per capita in the United States, where television had been introduced in the late 1940s. Correspondingly, homicide rates in the United States began to increase in 1959, while Finnish homicide rates did not begin increasing until 1969.4 According to Centerwall’s review,4 this pattern not only holds up for other countries but for regions within the United States as well: For the nine census regions of the United States, the timing of a region’s acquisition of television sets predicted the timing of subsequent increases in its homicide rate. Once television became an established medium available to virtually everyone in the United States, its effects became more difficult to document. Thus Comstock5 has noted that the remarkable aspect of television viewing is how much alike everyone is. The demographic differences in television viewing in the United States are overshadowed by the commonality of high viewing frequency: Almost every person watches almost every day. While the larger and more universal effects of a medium may be experienced with its introduction, however, the introduction of a new genre within a medium or of a variation or extension of a medium also seems to provide opportunities for distinguishing media effects. The debut of Dallas in the United States in 1978 marked the introduction of the nighttime soap opera as a television genre. The rapid diffusion of the program to other countries stimulated cross-cultural research concerning media involvement and cultural imperialism—the infiltration of alien values into a culture, possibly powerful media effects, as Katz6 has noted. Cable television and video recorders are examples of extensions of the television medium that provide viewers with opportunities for making more and new kinds of choices, thus providing researchers with new opportunities for examining the uses and gratifications obtained from television viewing. It seems likely that the removal of a medium or of a genre within a medium would also provide opportunities for distinguishing media effects. Media, media genre, and even particular programs are generally not removed, however, as long as there are sizable audiences for them: The case of tobacco advertising is an intriguing contradiction to this generalization. Tobacco advertising has been totally and “suddenly” banned in several cultures in which it was previously ubiquitous. Because tobacco advertisements were either the most prevalent or among the most prevalent ads in the countries in which they existed and because they have been trendsetters in genre style, specifically with image making, it seems possible that their removal would result in some detectable effect. If there are no discernible effects of tobacco advertising bans, then it seems probable that there are no discernible effects of tobacco advertising. The cross-cultural research described herein is part of a collaborative project concerned with reducing the initiation of smoking among youth in Finland and in the United States. The research has two broad objectives: (1) to consider how cultural differences affect the role that mass media may play in preventing smoking initiation, and (2) to determine how the presence or absence of tobacco advertising may play a role in the initiation of smoking. For both of these objectives the first step was to consider how current mass media use by Finnish youth compares with that of American youth.3,7,8 In the present study the authors examined the use of television, radio, newspapers, and magazines, and the attention to and enjoyment of advertisements (in general) as well as exposure to cigarette advertisements by Helsinki and Los Angeles youth between the ages of 8 and 15 years inclusively. Three questions were asked: (1) What mass media should be used to target youth in the two cultures for tobacco prevention and cessation programs? (2) How does the smoking behavior of Los Angeles youth compare with that of Helsinki youth? (3) Has the ban on tobacco advertising had a significant impact on youth in Helsinki?