The incidence of hypogonadism and use of testosterone replacement therapy (TRT) are rising, while data evaluating the complexity and quality of health-care information available to patients on the Internet for hypogonadism or TRT are lacking. This study focuses on characterizing the readability, credibility and quality of patient-centered information for hypogonadism on the Internet. A Google search was performed to identify top-ranked websites offering patient-centered information on hypogonadism and TRT. Readability was quantified by reading grade level using several validated instruments. Credibility and quality were determined by several additional criteria, including authorship, references, health-care information quality certification and breadth of topic discussion. Twenty of 75 total sites identified (27%) met the inclusion and exclusion criteria and were evaluated. The mean reading grade level was 13.1 (interquartile range 11.7-15.1), with all websites demonstrating reading levels significantly above recommended levels. Less than half (45%) of the sites were neither authored nor reviewed by a physician, 60% contained at least one reference and 40% were certified for displaying quality health-care information. Over half (55%) did not comprehensively discuss management of hypogonadism or mention treatment-associated risks. In conclusion, the majority of patient-centered information available on the Internet regarding hypogonadism or TRT is of poor quality and too complex for the average patient to comprehend. These results highlight a critical shortage in easily accessible, high-quality, comprehensible online patient health-care information on hypogonadism and TRT.