OBJECTIVES:  There is a dearth of evidence on factors influencing prescription plan switching versus switching from brand name drug to generic one. However, either of this switching decision could significantly impact health and wellbeing of Medicare beneficiaries. The objective of the present study was to better understand the relative impacts of individual versus prescription plan level characteristics on both of these switching decisions. METHODS: Medicare beneficiaries participated in the 2007 HRS prescription drug survey and 2009 HRS well-being survey and enrolled in Medicare part D (stand-alone), HMO, fee-for service or Advantage plans. The study sample includes 1298 individuals responded both years surveys. . Random intercept multinomial logistic regression model was estimated RESULTS: Only 5% of sample members switched into different prescription plans in both 2007 and 2009, while about 24% individuals switched from brand name drugs to generic product to save prescription drug costs. An outcome variable of interest includes 4 categories: switched into different part D plan, switch from brand to generic drug, thought about switching but did not actually switch and didn’t do anything. The main covariates of interest include individual and plan level characteristicsCompared to “didn’t do anything” Individuals were more likely to switch to different prescription plan (13%) or switched into generic drug from brand name (25%) if they were using higher number of prescription medications (p<0.04). Individuals having plans with good customer service was 54% less likely to switch into different part-D plan.  Compared to “didn’t do anything” individuals were 123% more likely to stay on the same plan being not satisfied with the current plan if they experience “inertia” in the plan choice decision CONCLUSIONS: Unobserved plan level characteristics matter in part-D plan switching or drug switching decisions. Consumer inertia and plan’s customer service quality appear to be important factors influencing these switching decisions