This study looked at the impact of Medicare Part D coverage gaps by examining drug discontinuation and reinitiation among Medicare beneficiaries using medications for cancer or rheumatoid arthritis. The study found that patients in the arthritis or cancer groups—28 and 21 percent, respectively—discontinued medications for these conditions in 2006; about three-fourths reinitiated therapy in the first 90 days of 2007. Although medication discontinuation is often temporary, the effect is complex. Some patients might discontinue before reaching the coverage gap to avoid out-of-pocket costs. For those who spend into or through the coverage gap before discontinuing, cumulative out-of-pocket expenditures might be too high to resume treatment the following year.