This study evaluated the impacts of two pharmaceutical cost containment policies-financial incentive for physicians to reduce pharmaceutical expenses and drug price cut- on physician prescribing during 2009~2012. Claims data for outpatient services in 1,625 clinics were drawn from national health insurance database between Jan. 2009 and Dec. 2012. Segmented regression analyses of interrupted times series were used to evaluate changes in pharmaceutical expenses, medical expenses, and prescribing patterns on therapeutic agents for most common diseases-gastric ulcer and gastro-oesophageal reflux disease(K25&K21), acute upper respiratory tract infections( J00~J06), acute lower respiratory tract infections( J20~J22), otitis media(H65, H66), cystitis and other disorders of urinary system(N30, N39), arthrosis(M15~M19)-in outpatient services. Monthly trend changes in pharmaceutical expenses were significantly reduced after the implementation of financial incentive program in Oct. 2010. Medical expenses and physician prescribing behaviors on therapeutic agents did not significantly change after the financial incentive program. Drug price cut in Apr. 2012 led to sudden decreases in pharmaceutical expenses in all diseases investigated. However, monthly trend changes in the pharmaceutical expenses after the price cut were significantly increased. Financial incentive on physicians was associated with continuous decrease of pharmaceutical expenses in outpatient services in clinics. Drug price cut caused instant reduction in pharmaceutical expenses, however the policy effect of price cut did not last after the sudden reduction. Further studies are needed to investigate which behaviors physicians changed to reduce their pharmaceutical expenses and whether the effects of financial incentive shown in this study continue in the longer time period.