Because many seniors choose Medicare Part D plans offering poorer coverage at greater cost, the authors examined the effect of price frames, brand names, and choice set size on participants' ability to choose the lowest cost plan. A 2×2×2 within-subjects design was used with 126 participants aged 18 to 91 years old. Mouselab, a web-based program, allowed participants to choose drug plans across eight trials that varied using numeric or symbolic prices, real or fictitious drug plan names, and three or nine drug plan options. Results from the multilevel models suggest numeric versus symbolic prices decreased the likelihood of choosing the lowest cost plan (-8.0 percentage points, 95% confidence interval=-14.7 to -0.9). The likelihood of choosing the lowest cost plan decreased as the amount of information increased suggesting that decision cues operated independently and collectively when selecting a drug plan. Redesigning the current Medicare Part D plan decision environment could improve seniors' drug plan choices.