It has an area of 4,000 sq. km. and a population of 62,637, all Catholic, distributed in 27 parishes served by 85 diocesan priests; a minor seminary; there are 14 women’s religious communities (Ann. Pont., 1951, p. 302).
The diocese was erected in the 13th century with its seat at Bisarchio as a suffragan of Sassari; it was suppressed in 1503 and united to Alghero; re-established on 5 March 1803 under the name Bisarchio; by decree of the Sacred Consistorial Congregation of 12 February 1915 the diocese changed its title to that of O. (AAS, 7 [1915], pp. 121–22).
The cathedral is dedicated to the Blessed Virgin Mary Immaculate; the patron saint of the diocese is St Antiocus.
BIBL.: P. Sella, Rationes decimarum Italiae nei secc. XIII–XIV (Studi e testi, 113), Città del Vaticano 1945, nn. 259, 901, 1745.