The GAA has confirmed that the personal details of over 500,000 members have been compromised following a data breach.
Servasport, which maintains the GAA database, revealed that there had been 'unauthorised access' to its database.
The database contains the names and addresses of 501,786 members.
Details include 288,511 dates of birth, 107,212 mobile phone numbers, 63,695 landline numbers and 30,171 email addresses.
The GAA says the database contained references to medical conditions of 544 members.
167,157 of the members on the database are under 18 years of age.
The Office of the Data Protection Commissioner, the GPA and the Information Commissioners Office in Belfast all received copies of the disk before informing the GAA.
It is understood the database did not contain any financial information.
Concerned members can contact a GAA helpline between 8am and 8pm on 1890-987807 (from the Republic) and 0800-0114787 (from Northern Ireland).