Former House speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) is to undergo surgery for treatment of an enlarged prostate untreated for years, his son said yesterday.

O'Neill, 74, was admitted to Sibley Memorial Hospital Monday after experiencing pain last weekend and is undergoing "testing for a lot of different things," said his son, Thomas P. O'Neill III of Boston.

He denied a report in The Boston Globe that his father's friends have been told that he is suffering from cancer.

The son said in a telephone interview that a decision on when to schedule surgery probably will be made Sunday morning.

He declined to elaborate on what tests have indicated about his father's condition, saying that he "feels very good" and is no longer in pain.

A hospital spokeswoman said only that O'Neill "is resting and in satisfactory condition."

He left Congress in January, ending a legislative career that began in 1936 with his election to the Massachusetts State House of Representatives. He was elected to Congress in 1952 and served as speaker in his last 10 years in Congress.

Since retiring, O'Neill has traveled extensively to promote his book, "Man of the House: The Life and Political Memoirs of Speaker Tip O'Neill." Friends have said that he has neglected to undergo treatment for an enlarged prostate.