Wildlife observability and responses and visitor attitudes were sampled after a mandatory visitor shuttle bus transportation system was in operation for 10 years in Denali National Park, Alaska. Visitor approval of the park transportation policy increased from 80% to 89% from 1972 to 1982-83. Vehicles per day increased 50% from 1973-74 to 1982-83. Moose sightings per trip declined 72%, grizzly bear sightings declined 32%, while Dall sheep and caribou sightings remained constant over the same period. Allowing unlimited private vehicle access during the falls of 1982 and 1983 had little influence upon the numbers of wildlife seen. However, more wildlife were put to flight, flight distances increased, more grizzlies were thwarted from crossing the road, and visitors stopped near and approached wildlife afoot more often. Wildlife responses were significantly influenced by pre-stimulus wildlife behavior for all four species, the type of human behavior for moose and grizzlies, sex/age class for moose and caribou, group size for caribou, number of vehicles present for grizzlies, and the presence or absence of vegetation screening for moose and grizzlies (p<0.05). Moose were alert four times as often (32±21%) when close to the park road than when >1 km away (4.8±5.1%), and when close to the road they were alerted to 37±21% of all road stimuli, while caribou were alerted to only 21±11% (p<0.03) of road stimuli.Key words: wildlife viewing, visitor attitudes, wildlife response to traffic, Denali National Park, moose (Alces alces), Dall sheep (Ovis dalli), grizzly bear (Urusus arctos), caribou (Rangifer tarandus)