As a result of the Penal Laws, which militated against the erection of chapels and regular record-keeping, Roman Catholic registers generally date from a later date than their Protestant counterparts, the majority dating from the 1820s. They relate almost exclusively to baptisms and marriages, though death or funeral entries do occur occasionally.

Original records are held in the parish of origin. The National Library of Ireland has microfilmed almost all of the pre-1880 registers and copies are held in the Public Record Office of Northern Ireland (MIC/ID). Microfilm copies are also held by the Church of Latter Day Saints.

Baptisms normally record:

• Date of baptism (normally takes place a few days after birth and therefore a satisfactory substitute for date of birth)
• Name of child
• Name of father
• Name of mother, including maiden name
• Names of sponsors
• Address of the family (in many cases).

Marriages normally record:

• Date of marriage
• Name of groom
• Name of bride
• Names of witnesses
• Names and addresses of parents (in some cases, especially from 1860s onwards).

Deaths/burials, if available, normally record:

• Date of death or burial
• Name of deceased.

In searching the records take account of all surname variants. Until well into the twentieth century there was no standardisation of the spelling of many surnames. The use of the prefix ‘O’ was based on personal preference and was not used by many record-takers in the nineteenth century.

Some Catholic registers make use of Latin but this is restricted to first names and is generally easily identified. Some of the more common names are as follows:

• Maria - Mary
• Brigida - Bridget
• Joannis - John
• Patricius - Patrick
• Jacobus - James
• Josephus - Joseph
• Gulielmus - William.

Other Latin terms and abbreviations which can be found are:

• de - of
• et - and
• filia/m - daughter
• filiu/m - son
• conji - married
• bapt - baptised
• sp - sponsors.