Ordained in 1984 in Guadalajara, Mexico, 
Bishop Gustavo Garcia-Siller, 46, was raised in San Luis Potosi, Mexico, where he attended grade school and high school. In 1973, he joined the Mexican Community of Missionaries of the Holy Spirit in Mexico City. He studied theology at the Major Seminary of the Archdiocese of Los Angles. By the time he was ordained, he had earned a degree in human development at the ITESO, a Jesuit University in Guadalajara, Mexico, and master's degrees in philosophy, theology and psychology.

Bishop Garcia-Siller worked with migrant workers on the border between the United States and Mexico. For 13 years, he was responsible for the formation of younger members of his religious order. He spent four years teaching in a high school and at the Institute for Philosophy in Guadalajara, also six years as rector of the order's House of Studies at Mount Angel, Oregon.

Bishop Garcia-Siller also served nine years in parish ministry. He spent four years in the Diocese of Fresno, California; two years in the Diocese of Orange,California; and three years in the Archdiocese of Portland.

Since 1999, Bishop Garcia-Siller has been head of his religious community, first serving as Major Superior and then as United States Provincial Superior a when the United States Province was formed earlier this year. He was appointed Titulas Bishop of Esco and Auxiliary Bishop of the Archdiocese of Chicago on January 24, 2003 by Pope John Paul II.