BUDAPEST, Hungary (AP) _ Former Communist Party leader Janos Kadar was hospitalized Monday with pneumonia and severe breathing and circulatory problems, the official MTI news agency said.

Kadar, 77, was listed in serious condition, the terse report said.

When Kadar was stripped of his last political posts in May after leading Hungary for 32 years, senior communist leaders said he was gravely ill, but they did not specify the ailment.

In May 1988, Kadar was named honorary chairman of the ruling Hungarian Socialist Workers' Party, which he had led since Kremlin troops and tanks crushed an anti-Soviet revolt in 1956.

Under Karoly Grosz, who succeeded Kadar as party general secretary but has himself been forced to share power with three prominent party reformers, Kadar's political legacy increasingly has come into question.

After guiding Hungary to relative prosperity and tolerance by the 1970s, Kadar was seen as an obstacle to political and economic reform in the 1980s.

Questions remain about Kadar's role at the end of the 1956 revolt. He emerged as head of a new government to replace that of premier Nagy as the uprising was violently crushed.

In recent interviews published by the weekly Magyarorszag, Kadar was quoted as saying the fate of Imre Nagy and other revolt leaders was his ''personal tragedy.''

Nagy and other leaders of the uprising were honored as national martyrs June 16.

Kadar was last reported to have attended a Communist Party Central Committee meeting in April, where other participants said he gave a long, rambling speech.

A letter sent to Kadar accused him of making mistakes during his rule. Kadar, who has not been seen in public since, replied in a published response that he had always acted only for the good of Hungary.