Since 1992 more than 5000 churches from various denominations have joined the Willow Creek Association through its U.S. office and 13 international affiliates. Membership and conference attendance are open to churches and leaders who "hold to a historic, orthodox understanding of biblical Christianity." Evangelism, leadership, the arts and worship,and student ministry are topics for both conferences and publications produced by the association. Books, videos, music, training courses, and other resources published by Willow Creek are discounted for churches that are association members. Reaching out to the unchurched is a focus of this ministry.