OBJECTIVES: Those patients visited toward a single hospital loyally have accounted for 3.5% of all beneficiaries and consumed 19.3% of covered medical expenditure under Taiwan’s National Health Insurance (NHI) program. This study was to examine the trends of service utilization, medical expenditure and disease patterns among loyal patients visited toward China Medical University Hospital (CMUH), a 2000-bed medical center in Taiwan.  METHODS: Patients’ visits made toward CMUH accounted for more than 50% of their total outpatient visits in Taiwan during January 2008 to June 2009 (retrospective period) were assigned as CMUH loyal patients by Bureau of NHI. The corresponding data documented in CMUH from January 2008 to April 2010 were retrieved and analyzed. Those assigned loyal patients persistently visited CMUH during July to September 2009 were grouped into four levels of utilization base upon their numbers of outpatient department (OPD) visits made toward CMUH during retrospective period. The comparisons of disease statuses, healthcare utilization, medical expenditure and visits toward different specialties among different utilization groups and across different study periods in CMUH were made. RESULTS: 11,846 CMUH loyal patients were groups into four levels of OPD utilization (<20, 21~23, 24~35, >36) during 18 months (mean OPD visit =1.83/person/month). Those loyal patients used more OPD visits were elder, more co-morbidities, taken care by more physicians and medical specialties, and prescribed more medications. The more visits made toward OPD, the higher likelihood to consume more medical expenditures and utilize more medical resources in CMUH. Although more than 75% of OPD visits were made toward one or two medical departments, more medical resources in CMUH were attributable to those patients visited more than three medical specialties.  CONCLUSIONS: Results suggest in-house programs to facilitate integrated care and medication reconciliation toward high utilization loyal patients are more demanded than other loyal patients in CMUH.