OBJECTIVE: This paper explores the characteristics associated with decisions to adopt or discontinue the use of filtering software, including a critical analysis of some explanations about why it is used or not used in households with children and adolescents. METHOD: This study consisted of a national telephone survey of households in the United States with youth (10 and 17 years) who use the Internet regularly. Interviews were completed with one youth in the appropriate age group and a parent or caretaker. RESULTS: Thirty-three percent of parents reported using filtering or blocking software, with an additional 5% having discontinued its use within the past year. Parents were more likely to adopt filtering software if they had younger children (10--15 years), a high level of concern about exposure to sexual material on the Internet, more extensive knowledge of what their child did online, low trust in the child's ability to use the Internet responsibly, and if the child used America Online (AOL). Using the Internet for school assignments was associated with not having filtering software. CONCLUSION: Findings suggest the need for (1) evaluation research of filter programs used in a real family context and (2) the development of a variety of strategies to prevent exposure to inappropriate material for youth of different ages.