Northern Ireland's Democratic Unionist Party (DUP) leader has spent the night in hospital after suffering an adverse reaction to medication.
Peter Robinson, 66, who suffered a heart attack in May, was admitted to Belfast's Royal Victoria Hospital on Saturday.
A DUP spokesman said he was doing well.
"Mr Robinson had a reaction to some medication and was admitted as a precautionary measure.
"He is doing well and will be discharged soon."
A spokesman for the RVH confirmed Mr Robinson had been admitted on Saturday night.
He said: "Peter Robinson was admitted to the Royal Victoria Hospital as a precautionary measure.
"He is comfortable and is doing well."
Mr Robinson, who has endured a punishing schedule in recent weeks, has temporarily stepped aside as First Minister following a political crisis sparked by the murder of former IRA man Kevin McGuigan last month.
His unexpected health problems come ahead of Monday's crunch talks aimed at saving the devolved Assembly at Stormont.
In May he spent four nights at the RVH after suffering a suspected heart attack and had three stents fitted to help the flow of blood.
At the time, Mr Robinson blamed his illness on an unhealthy lifestyle rather than the stress of his job.