We conducted a prospective cohort study of 886 consecutive patients with basal or squamous cell skin cancer who completed an in-person questionnaire before treatment. Office treatments for NMSC included Mohs surgery, excision, and destruction with cryotherapy or electrodessication and curettage. At 3, 12 and 18 months and annually up to 5 years after treatment, patients were asked: “In your opinion, have there been any complications of your treatment during or after the treatment itself?” Those who reported a complication were asked to describe it and to rate its severity using a Likert-like scale ranging from minimally to extremely serious. Descriptions were classified by 2 independent clinicians into 2 categories: 1) medical complications: bleeding, infection, pain, swelling, poor wound healing, numbness or itching, problem with motor function, allergic reaction to bandages or antibiotics, and 2) non-medical problems: problems with scar or appearance, need for additional treatment, administrative problems or other. Overall, 83% of patients responded to at least one questionnaire. We calculated complication rates as the number of patients out of our baseline cohort who reported a complication at any time point, making the conservative assumption that all non-responders including patients lost to follow up did not experience complications. Two clinicians reviewed all medical charts for complications up to 5 years after treatment.