In the same year he was sent to undertake the Christianization of the Ahome and Suaqui of northern Sinaloa, of whom the former were friendly and anxious for teachers, while the latter had just been brought to submission after a hard campaign.
Within a year he had both tribes gathered into towns, each with a church, while all of the Ahome and a large part of the Suaqui had been baptized.
In 1613, being then superior of the Sinaloa district, he was instrumental in procuring the submission of a hostile mountain tribe.
In 1617, in company with other Jesuit missionaries whom he had brought from Mexico City, he began the conversion of the powerful and largely hostile Yaqui tribe of Sonora, whose population was estimated at 30,000.
After a visit to Rome in 1643 to take part in the election of a general of the order, he devoted himself chiefly to study and writing until his death.