The creation of the National Health Insurance program has greatly contributed to giving Japan the world’s highest level of life expectancy.  However, the cost of medical care in Japan has increased as a result of an aging society.  In response to this reality, the Japanese government initiated a campaign to promote the use of generic drugs (GEs).  In order to clarify some of the trends that contribute to different clinical medicine department usages of GEs, we carried out a survey of 400 pharmacies.  The survey data was analyzed using linear regression analysis.  Analysis of linear equations derived “utilization” that indicated ease of use of GEs, and a “saturation acceptable value (maximum allowed)” that indicated usage of GEs.  The breakdown for different clinical medicine department usages of GEs was determined as the following: psychosomatic medicine or psychiatry was 11±0.13%, internal medicine was 29±0.18%, orthopedics was 18±0.14%, ophthalmology or otolaryngology was 15±0.14%, other departments was 17±0.15%.  Furthermore, the highest utilization derived by linear regression analysis was orthopedics.  The highest acceptable saturation value was for psychosomatic medicine or psychiatry, while the lowest acceptable saturation value was orthopedics.  The results of the study confirm the importance of establishing evaluation methods for GE usage, and that linear regression analysis is a powerful tool for revealing trends in GE usage among different departments.  Additionally, the study suggests that determining GE spread measures is valuable, since they can serve as an aid to future pharmaceutical administration consideration.