Objective: Previous research has shown that exposure to unemployment could have health effect and income effect on medical care utilization. This study examines total and five disease-specific medical care utilizations before and after exposure to involuntary unemployment under the National Health Insurance Program in Taiwan. Methods: An experimental study with control group and fixed effect model were used. Two groups of people were observed from 1999 to 2002: (1) the involuntary unemployment group (n=92,562), and (2) the control group (n=92,443). The unit of observation was person-year. In order to obtain more precise estimates and control for possible confounders, the difference-in-difference (DD) method and generalized estimation equation (GEE) approach were conducted. Results: Decrease in both ambulatory and inpatient services utilizations were observed after unemployment. In terms of disease-specific utilization, 3 important findings are identified: (1) a decrease in the ambulatory utilization for respiratory diseases has been detected after unemployment; (2) no significant change in utilization for three cardiovascular diseases has been found after unemployment; (3) an increase in utilization has been identified for mental diseases after unemployment. Conclusion: A decrease in income and health effects of unemployment on medical care utilization vary among the types of diseases. One limitation in the study that we only examined the short-term (one year) effects of unemployment on medical care utilization, so it is important in the future to further investigate the possible long-term effects of unemployment on utilization.