Objectives: Consumers rely on online health information, particularly for unusual conditions. Disorders of Sex Development (DSD) are complex with some aspects of care controversial. Accurate web-based DSD information is essential for decision-making, but the quality has not been rigorously evaluated. The purpose of the present study was to assess the quality of online health information related to DSD presented by 12 pediatric institutions comprising the NIH-sponsored DSD-Translational Research Network (DSD-TRN). Methods: DSD-TRN sites identified team webpages, then we identified linked webpages. We also used each institution search engine to search common DSD terms. We assessed webpages using validated tools: the Simple Measure of Gobbledygook (SMOG) determined reading level, the Patient Education Materials Assessment Tool (PEMAT) evaluated content for understandability and actionability, and the DISCERN tool assessed treatment decision-making information (for hormone replacement and surgery). We developed a "Completeness" measure which assessed the presence of information on 25 DSD topics. Results: The SMOG reading level of webpages was at or above high-school grade level. Mean (SD) PEMAT understandability score for Team Pages and Team Links was 68% (6%); on average these pages met less than 70% of the understandability criteria. Mean (SD) PEMAT actionability score was 23% (20%); few patient actions were identified. The DISCERN tool determined that the quality of information related to hormone treatment and to surgery was poor. Sites' webpages covered 12-56% of the items on our Completeness measure. Conclusions: Quality of DSD online content was poor, and would be improved by using a variety of strategies, such as simplifying word choice, using visual aids, highlighting actions patients can take and acknowledging areas of uncertainty. For complex conditions such as DSD, high-quality web-based information is essential to empower patients (and caregiver proxies), particularly when aspects of care are controversial.