Data from six deep gas wells in Wyoming indicate that foamed cement outperforms conventional cement for zonal isolation. Two wells that were cemented across the production zones with conventional nonnitrified cements experienced outer-zone communication after stimulation treatments. In the other four wells, the foamed-cement sheath provided zonal isolation even after the sheath was perforated and stimulation treatments were performed. Case histories described in the full-length paper compare foamed-cement performance with conventional cement performance in similar wells in the same geographic area.