The purpose of this systematic review was to (i) estimate the prevalence and dose of television (TV) viewing, video game playing and computer use, and (ii) assess age-related and (iii) secular trends in TV viewing among youth (< or = 18 yr). Ninety studies published in English language journals between 1949 and 2004 were included, presenting data from 539 independent samples (the unit of analysis). Results suggest contemporary youth watch on average 1.8-2.8 h of TV per day, depending on age and gender. Most (66%) are "low users" (< 2 h day(-1)) of TV but 28% watch more than 4 h day(-1). Boys and girls with access to video games spend approximately 60 and 23 min day(-1), respectively, using this technology. Computer use accounts for an additional 30 min day(-1). Age-specific data suggest TV viewing decreases during adolescence, but those considered "high users" at young ages are likely to remain high users when older. For children with access to a television set, the number of hours spent viewing does not appear to have increased over the past 50 years.