Around 80% of Sumba’s 550,000 inhabitants are Christians. Most belong to the Christian Church of Sumba - Gereja Kristen Sumba (GKS) - which has been growing steadily since the 1980s. The Church is run through a five-person leadership team chosen to represent the General Synod.

Leadership development is a key priority.  Many congregations are vacant; others are oversized.  Along with presbyteries, they are slowly being subdivided into a more manageable size.  GKS also faces the challenge of improving skills of existing staff, developing new leaders at all levels and placing the many assistant ministers currently preparing for ordination.

The Practical School of Theology (PTTG) was founded in 2005 to train 200 new lay workers over four years; its first graduates began service in 2008.  GKS also runs two hospitals, a number of primary and secondary schools and opened a new professional training centre in 2007.