There is no question that over the last thirty years environmentaldegradation and the ecological crisis have become in our day and age apredominant sign of the times. In response to this worrisome develop-ment official documents of the Roman Catholic Church, at various lev-els, have sought to address the growing ecological concern from theperspective of Catholic social teaching. Consequently references to ecol-ogy and environmental issues have surfaced in papal encyclicals duringthe last fifteen years generating national and regional responses. In theUnited States, for example, the U.S. Conference of Catholic Bishops hasissued two pastoral statements on environmental issues in 1991 and2001. Significantly, the Catholic Bishops of the Pacific Northwest, rep-resenting Canada and the U.S. have also issued a unique internationalletter focused on a particular ecological region—the Columbia RiverWatershed. What all of these efforts hold in common is the attempt toapply Catholic social teaching to a new and disturbing phenomenon inhuman experience. The result has been an expansion of Catholic socialthought. What was once the “social question” has now become the socialand “ecological question.” This development, the effort to address ecol-ogy and environmental issues as ethical problems, is the focus of thispaper. In particular this paper will link environmental and humanecology with the concept of sustainability, with the intention of propos-ing an interpretation of the common good and a definition of sustain-ability within Catholic social teaching.