The authors report two cases of Mycobacterium paratuberculosis infection in free-ranging Alpine ibex (Capra ibex) from two different herds in the Western Alps, Italy. One ibex, found dead in October 1998, was in poor condition. The second animal died due to trauma following capture with a dart gun. The only gross lesions observed were the enlargement of the mesenteric and iliac lymph nodes. Samples from both ibex tested positive to polymerase chain reaction for a primer set specific for the M. paratuberculosis insertion sequence IS900 and one ibex also tested positive to the Zielh-Nielsen stain. Isolation by bacterial culture was not successful. The infected ibex originated from herds in which seroreactors to M. paratuberculosis had been found previously. Seroreactors to M. paratuberculosis were also detected in sympatric cattle.