The effect of seasonal cattle grazing on a newly reintroduced vii population of California bighorn sheep (Ovis canadensis californiana) in Big Cottonwood Canyon, Idaho, was studied. The hypothesis that bighorn sheep avoid cattle was tested. The issue of avoidance between bighorn sheep and livestock is arguable. Some studies have found that bighorn sheep avoid cattle while others have found no response of bighorn sheep to cattle. Evidence was found to document the avoidance of cattle by bighorn sheep. The size of the bighorn's home range and core area decreased with the movement of cattle into areas of high bighorn use. As cattle were moved into bighorn core areas, sheep responded by relocating. Bighorn sheep decreased their distance to escape terrain as cattle moved closer. The level and location of human disturbance on the study area did not have any effect on bighorn sheep movements or how sheep used the habitat. The severity of response observed is in marked contrast with the response of established bighorn populations to cattle. I suggest that newly reintroduced bighorn sheep are extremely sensitive to disturbance as a result of relocation trauma. Sensitivity may diminish over time.