Exposure to onscreen smoking in movies increases the probability that youths will start smoking. Youths who are heavily exposed to onscreen smoking are approximately two to three times more likely to begin smoking than youths who are lightly exposed; a similar, but smaller effect exists for young adults. To monitor the extent to which tobacco use is shown in popular movies, Thumbs Up! Thumbs Down! (TUTD), a project of Breathe California of Sacramento-Emigrant Trails, counted the occurrences of tobacco use (termed "incidents") shown in U.S. top-grossing movies during 1991-2009. This report summarizes the results of that study, which found that the number of tobacco incidents depicted in the movies during this period peaked in 2005 and then progressively declined. Top-grossing movies released in 2009 contained 49% of the number of onscreen smoking incidents as observed in 2005 (1,935 incidents in 2009 versus 3,967 incidents in 2005). Further reduction of tobacco use depicted in popular movies could lead to less initiation of smoking among adolescents. Effective methods to reduce the potential harmful influence of onscreen tobacco use should be implemented.