Forty years ago, David B. Barrett, then based in Nairobi, Kenya, put the finishing touches on the first edition of the World Christian Encyclopedia. A second edition was produced in 2001, and now a third edition is in circulation, prepared between 2015 and 2019. This special issue of the IBMR reflects a core part of the methodology of the World Christian Encyclopedia, namely, interaction with World Christianity from different disciplinary perspectives and geographic locations. This introduction to the issue features reflection on articles on global Catholicism, missions, women and gender studies, religious freedom, Christianity in the Middle East, and refugees.