Each September the park hosts a four-day event called "Road Lottery." During these four days, winners of a lottery drawing are given a chance to purchase a single, day-long permit, allowing them to drive as much of the Denali Park Road as weather allows. Applicants must apply for the lottery between June 1 - June 30, 2011, to partake in the September 2011 Road Lottery.
http://www.nps.gov/dena/planyourvisit/road-lottery.htm
http://www.nps.gov/dena/planyourvisit/road-lottery.htm