This study investigated how sociological variables, program access, family attributes, and child characteristics influence children's viewing of the most well-established educational television program in the United States--"Sesame Street." 2 cohorts were followed from ages 3 to 5 and 5 to 7, respectively. Each family kept a diary of television viewed during 5 1-week periods over 2 years. Interviews and testing sessions were conducted before and after the 2-year period. "Sesame Street" viewing increased from age 3 to a peak between the ages of 3 1/2 and 4; thereafter, viewing declined. This developmental change appeared to be a function of age-correlated life events and perceived age appropriateness of the program rather than of ontogenetic cognitive change. Individual differences were primarily a function of family ecology--opportunities to view and characteristics of other viewers--rather than of family demographics or individual child attributes. Maternal employment and the amount of time children attended child care or preschool were negatively related to viewing. The presence of older siblings reduced viewing; the presence of younger siblings increased it. Viewing was unrelated to parent education or occupational status, child gender, child's vocabulary level, involvement in television, or interest in print and other media. Parental encouragement to watch the program was positively related to viewing for 3-5-year-olds.