Iarnród Éireann has warned that further disruption to services is expected today because of the unofficial industrial action by some train drivers.
The nature of the action means it is not possible for the company to be precise about what services are affected, a spokeswoman said.
However, services operating from Heuston Station in Dublin and Cork's Kent Station are again expected to be the most severely affected.
Some disruption is also expected to services between Heuston and Limerick/Ennis, Galway, Westport and Waterford.
The Portlaoise and Kildare commuter services to Dublin are also under threat.
There was no disruption yesterday to services in and out of Connolly Station in Dublin, and it is hoped these will again run normally today.
Iarnród Éireann advises that intending passengers check for updates on the company's website, www.irishrail.ie, or call its information line on 1850 366222.
