All of the women had participated in a 2-year trial that had compared benefits of placebo [dummy pills], Premarin, alendronate, and combination therapy. At the end of the trial, they were given the opportunity to participate in a 1-year study of stopping therapy. Those who agreed were divided into five groups. The groups switched to placebo from 1) alendronate, 2) Premarin or 3) combination therapy, or they continued 4) placebo or 5) combination therapy. The women had bone mass measurements with special x-rays at 6-month intervals. The researchers then compared bone mass between groups.