The purpose of this study is to determine the feasibility and efficacy of a behavioral intervention, delivered through an existing social networking website (Facebook), on physical activity (moderate-intensity minutes per week) among young adult cancer survivors compared to a self-help education condition. For this research study, investigators will conduct a 12-week randomized trial. After a baseline survey, weekly messages, a pedometer, goal-setting tool, physical activity log and discussion prompts will be delivered to the intervention group. Comparison group participants will receive links to websites with self-help education materials. After 12 weeks, a follow-up survey will be given to both groups. Changes in physical activity, quality of life and psychosocial factors will be examined. The investigators hypothesize that those receiving the intervention will have improved physical activity behaviors at 12-week follow-up relative to those in the comparison group.

Inclusion Criteria:

• Young adult between ages 21-39 diagnosed with cancer (excluding non-melanoma skin cancer) at age 18 or older
• At least 1 year beyond date of diagnosis with no evidence of progressive disease or second primary cancers
• Completed cancer treatment
• English-speaking and writing
• No pre-existing medical condition(s) or contraindications that preclude adherence to an unsupervised exercise program, including cardiovascular disease, congestive heart failure, pulmonary conditions, renal disease, and severe orthopedic conditions
• Not adhering to the American Cancer Society's recommendation of at least 150 minutes of moderate-intensity exercise per week (<150 minutes/week)
• Have access to Internet service and an active Facebook account
• Willing to be randomized
• Have indicated consent by checking "yes" to the online consent form

Exclusion Criteria:

• Non-English speaking
• < 21 and > 39 years of age
• Diagnosed with cancer less than one year previously or still in treatment
• Pre-existing medical condition(s) that preclude adherence to an unsupervised exercise program, including cardiovascular disease, congestive heart failure, pulmonary conditions, renal disease, and severe orthopedic conditions