We documented hybridisation of domestic goats Capra aegagrus domestica with free-ranging male Alpine ibex Capra ibex ibex in a restricted area of the southern Swiss Alps in 1989–2001. The number of animals in the hybrid herd reached a maximum of 18 in 1998. We confirmed hybridisation through morphological data and genetic analysis. All presumed hybrids were larger and heavier than Alpine ibex. Horns of hybrids were longer than those of Alpine ibex, and some male horns lacked nodes. In two males studied, the first horn increment was longer than the second. In some cases the pelage colour revealed characteristics untypical for ibex such as prominent leg markings and dark brown colour in young animals. Microsatellite analysis in one male revealed ibex specific alleles as well as goat specific alleles. We concluded that this male, as well as the other animals studied, were Alpine ibex x domestic goat hybrids. All wild goats and their hybrid offspring were removed by state gamekeepers in 1998–2001 to maintain the genetic integrity of free-ranging Alpine ibex living in the area. We suggest that the survival of hybrids depends largely on habitat characteristics. In the study area, the hybrid winter range was exposed to the south. The sunny rocky slope was steep and reached down to an altitude of 1,500 m a.s.l. On this slope, animals found food in early spring and a refuge against adverse weather conditions.