Ken and Rita have served as missionaries in Vicente Guerrero, Mexico since 1999. Ken is the senior pastor of Calvary Chapel (Capilla Calvario) Vicente Guerrero. Rita oversees children's ministry as well as women's ministry. The Marrs minister primarily to three unreached tribal groups: Triqui, Mixteco, and Zapotec. (Ken and Rita have four adult sons who live in the United States. Their 17 year-old daughter Alejandra, lives with them in Mexico.)
The Marr's ministry verse is John 17:3. It is from the prayer of Jesus to His Father: "And this eternal is life, that they may know You the only true God, and Jesus Christ who you have sent."