Purposes: Outpatients Appointment system can provide better service, increase patients' accessibility to doctors and improve efficiency of medical care. The aim of this study was to investigate the non-attendance rate and its associated factors in patients with follow-up appointment at Family Practice Clinics of a medical center.Methods: The rate of non-attendance was calculated by the number of non-attendance divided by the number of total patients with follow-up appointment in the department of family medicine in a medical center from March 1 to 31, 2003. We further conducted a case-control study, including 199 non-attendances and 396 attendances, to determine the associated factors of non-attendance.Results: The overall non-attendance rate was 6.2% (298/4,807). The non-attendance rate in resident's clinics was 10.18% (86/845) which was higher than that of visiting staff's clinics (5.35%, 212/3,962). Of the 199 non-attendance, 147 and 52 were recruited from visiting staff's and resident's clinics, respectively. Of the 396 attendances, 269 and 127 came from visiting staff's and resident's clinics, respectively. Univariate analysis showed that the non-attendances were younger and had higher rates of not-receiving the next visit information from clinic assistant, were unaware of appointment cancelling procedure, and perceived of the follow-up visit was troublesome and unnecessary in subjects from both visiting staff's and resident's clinics. Furthermore, there were significant differences in the proportion of appointments scheduling with Family Practice or with others and subjects with or without chronic diseases having refill prescription. In addition, the proportion of perceiving expensive visiting cost was higher in nonattendance than attendance at resident's clinics. Based on multiple logistic regression analysis, not-receiving the next visit information from clinic assistant, absence of chronic diseases, presence of chronic diseases without refill prescription, unaware of appointment cancelling procedure, perception of the follow-up visit was unnecessary were positively related to nonattendance at visiting staff's clinics. At resident's clinics, the following were the positively associated factors of non-attendance: not-receiving the next visit information from clinic assistant, unaware of appointment cancelling method, perception of follow-up visit was expensive; but age was the negatively associated factors.Conclusions: Clinically, the following may decrease the non-attendance rate: 1) visiting staff may offer refill prescription, if patients' chronic diseases are stable and 2) clinic assistants provide the information of the next visit and the appointment cancelling method if necessary.