The objective of the current study was to evaluate the content and quality of patient-oriented information regarding intensity-modulated radiotherapy (IMRT) on the Internet.IMRT websites were identified by reviewing the first 50 uniform resource locators on 5 search engines using the search terms IMRT and intensity modulated radiation therapy. Each site was evaluated by three observers for informational content, presentation, accuracy, and balance. A score of low, moderate, or high was assigned to each category based on a predefined scoring system. An overall score was assigned to each site, ranging from -35 to 100 points.Seventy-seven patient-oriented IMRT websites were identified (45% private, 21% academic, and 18% commercial). Most sites (58%) had a low level of informational content, with information on fundamental aspects of IMRT planning (target delineation and inverse planning) appearing on < 50% of sites. The most commonly discussed tumors were genitourinary (65%) and head and neck (53%) lesions. Few sites, however, described the potential benefits of IMRT (toxicity and tumor control). Most sites (82%) used patient-appropriate language. False and/or misleading information was seen on 42% of sites and was equally common on academic, private, and commercial sites. Balance statements were present on 24% of sites (most of which were commercial). The median overall score was 20 points (range, -25 to 70 points). The median overall scores for academic, private, commercial, and other sites were 10, 20, 25, and 20 points, respectively (P = 0.26).In general, the content and quality of patient-oriented information regarding IMRT on the Internet were poor. Patients and their physicians need to be aware of these problems when selecting treatment courses.