Background: Patients may be at risk for significant late effects after multimodality therapy for gastric and esophageal (GE) cancers, the impact of which may be difficult to evaluate using conventional methods. This Internet-based study evaluates patient perceptions of toxicity after treatment for GE cancer. Methods: Patient-reported data was gathered via a convenience sample frame from GE cancer survivors voluntarily utilizing a publically available, free, Internet-based tool for creation of survivorship care plans. Available at www.livestrongcareplan.com and through the OncoLink website, the tool allows survivors to enter data regarding diagnosis, demographics, and treatments, and provides customized guidelines for future care. During use of the tool, GE cancer survivors are queried regarding late effects associated with specific treatments. All data have been maintained with IRB approval. Results: Sixty-six GE cancer survivors answered queries regarding late effects; 62% were female and 93% Caucasian. Median diagnosis age was 55 yrs (19–74 yrs), median current age 59 yrs (19–77 yrs), and average time since diagnosis 3.8 yrs. Most reported having had multimodality therapy—88% surgery, 80% chemotherapy, and 48% radiation. When queried regarding persistent health problems after cancer treatment, 35% reported cardiovascular disease (21% hypertension, 13% hyperlipidemia, 3% angina), 28% sexual dysfunction, 36% tinnitus, 24% peripheral neuropathy, 42% cognitive changes, 100% difficulty swallowing, 60% dry mouth or taste changes, 40% dental changes, and 14% chronic lung disease. Conclusions: Survivors using this tool anonymously and voluntarily report significant health problems after treatment for GE cancers. The data reported here may be of significant impact in future study of quality of life, as well as patient counseling and survivor care.