Purpose: This paper aims to analyze the demographic and prosthodontic treatment differences between patients who did and did not respond to a mailed questionnaire. Materials and Methods: All living patients who received tooth- and implant-related fixed prosthodontic treatment between January 1984 and June 2005 (n = 986) in one private prosthodontic practice were mailed a questionnaire regarding their prosthodontic treatment. Demographic data (sex, age) and treatment data (survival, type of treatment, time in situ, number of units, number of treatments) for responding and nonresponding patients were collected from patient files and analyzed. Statistical significance was set at P = .05. Results: There were 500 responding patients (50.7%) with 2,702 fixed prosthodontic units (60.02%) and 486 nonresponding patients (49.3%) with 1,800 fixed prosthodontic units (39.98%). Prostheses were in situ from 1 to 20 years, with the average time in situ for respondents of 7.47 ± 5.48 years and 6.5 ± 5.21 years for nonrespondents. Responding and nonresponding patients had similar sex distributions (P = .61), Kaplan-Meier 10-year estimated cumulative survivals (92.2 ± 1.72% and 91.5 ± 1.92%; P = .13), and received a similar distribution of treatment prostheses (implant versus tooth) (P = .24). However, responding patients were significantly older (P .001), had their prostheses in situ for a greater length of time (P = .01), received more prosthetic units (P .001), and underwent more treatment episodes (P .001) than nonresponding patients. Conclusions: Patient questionnaires provide valid and unique research information. Prosthesis outcomes for patients who did and did not respond to the questionnaire were the same. Treatment outcomes of patients who attend review appointments and those who are lost to follow-up cannot be assumed to be different. Demographic- and treatment-related characteristics of responding patients indicated that an enhanced provider-patient rapport was a principal motivator for responding to the questionnaire.