OBJECTIVE: To examine the relationship between the use of preventive software on the home computer and unwanted exposure to sexual material online. METHODS: The Youth Internet Safety Survey-2 was a national, RDD telephone survey conducted in March-June 2005. Eight hundred households (one caregiver and one child between the ages of 10 and 17 years) with home Internet access answered questions pertaining to Internet prevention activities in the household and adolescent behaviors and exposures online. RESULTS: Unwanted exposure to sexual material occurred in 32% of youth in homes with pop-up/spam blockers and 25% of youth in homes with filtering, blocking, or monitoring software on the home computer, compared to 43% of households without preventive software installed on the home computer. Among otherwise similar youth, pop-up/spam blockers installed on the home computer were significantly associated with 59% lower odds of reporting unwanted exposure to sexual material on the home computer; and filtering, blocking, or monitoring software was significantly associated with 65% lower odds. When data were stratified by youth sex, associations between preventive software and unwanted exposure were similar for boys and girls. When stratified by age, preventive software was associated with significantly reduced risk of unwanted exposure for 10-12-year olds and 13-15-year olds, but not for 16-17-year olds. CONCLUSION: Although these correlational analyses are far from providing conclusive evidence that preventive software protects children from unwanted exposure to sexual material online, findings suggest that caregivers of boys and girls 15 years of age and younger who want to reduce the likelihood of unwanted exposure to sexual material on the home computer should consider including preventive software-especially filtering, blocking, or monitoring software-in their Internet safety plan. PRACTICE IMPLICATIONS: Practitioners should partner with caregivers in developing an Internet safety plan, including proactive caregiver-youth discussions about expected Internet behavior appropriate for their household.