It was erected on 13 January 1949, by separating the territory from the Apostolic Vicariate of Miarinarivo. It is entrusted to the Trinitarian Fathers. On 9 June 1950, another territory was added to it from the Apostolic Prefecture of Morondava.
It has an area of 40,000 sq. km. with 63,500 inhabitants, of whom 10,503 are Catholics, 7,500 catechumens, 11,000 Protestants, 32,500 pagans, and 1,500 Muslims. There are 10 missionaries, 3 brothers, 2 sisters, and 120 catechists. There are 4 primary stations, 126 secondary stations, 13 churches, and 70 elementary schools.
BIBL.: AAS, 41 (1949), pp. 214-155; 42 (1950), p. 891; MC, 1950, pp. 202. Saverio Paventi