Czech Health Minister David Rath has been in a punch-up with his right-wing rival, Miroslav Macek, during a meeting of disgruntled dentists in Prague.
Mr Macek, a presidential adviser and former deputy PM who is also a dentist, broke off an address to slap Mr Rath hard on the back of the head.
Mr Rath responded by calling him a coward and the two men traded blows.
This rare case of violence in Czech politics comes two weeks before highly anticipated parliamentary elections.
The meeting of dentists, at which Mr Macek was moderator, took place at the start of a period of planned protest against Mr Rath's policies, dubbed "A Week of Healthcare Unrest".
But, says BBC Prague correspondent Rob Cameron, no-one had envisaged the unrest going quite this far.
'Coward'
Mr Macek took the stage to begin the discussion.
But before he did so, he explained to the audience there was a private matter he had to settle with Mr Rath first.
He walked up behind him and slapped him, hard, on the back of the head.
The audience watched in amazement as a stunned Mr Rath rose and made to leave.
But then the health minister turned on his heels, walked up to Mr Macek and called him a coward.
Mr Macek responded by hitting him again, and the two men began throwing punches.
Mr Macek explained he slapped Mr Rath because he made comments about his wife.
But this incident, between senior members of the country's two leading political parties, comes less than two weeks before parliamentary elections.
Our correspondent says election campaigns in the Czech Republic are usually rather dull affairs - but this year's are proving anything but boring.