| Diest: Sulpitiuskerk |
The oldest parish of Diest; from 1163 onwards served by Tongerlo abbey. A chapter of 13 canons was founded in 1457 by the abbot of Tongerlo and the prince-bishop of Luik (Mon. Belge VIII, p. 309); one of the premonstratensians of Tongerlo functioned as parish priest of the church and was a the same time provost of the chapter. The chapter was disbanded in 1797.
Patron: Sulpitius II Pius of Bourges. At present the church is called Sulpitius- en Dyonisiuskerk.
Some manuscripts are still preserved in the church:
 | Leaf of a Sacramentarium, 12th century |
| | Oath book, 1493-94 |
Several manuscripts have incorrectly been attributed to this church: first the two books mentioned below, and secondly B-LVap 20, a 13th century Missal.
At present several books are kept in the church, belonging to Mariëndaal in Diest:
 | B-D Graduale s.n., mid 15th - early 16th century |
| | B-D Antiphonarium s.n., 1470-1480 |
 | Handschriften uit Diestse kerken en kloosters |
| | Saints in Brabant, pp. 14-20 |