Mario Chiesa scored the crucial goal for Parma in the second minute of a violent match in which each side had two players sent off. It was the second successive surprise victory for Parma, who beat the champions, Milan, just before the Christmas break.
Vicenza, 2-0 home winners over Bologna thanks to two strikes from Marcelo Otero, took sole possession of second place on 26 points, three points behind.
Sampdoria, 5-4 winners over Udinese, and Internazionale, who beat Roma 3-1 in Milan, are joint third on 25 points.
In Spain, an 87th-minute strike by the substitute Juan Pizzi gave Barcelona a well-deserved 1-0 victory at Deportivo La Coruna. The game marked the re-emergence of the Brazilian striker Ronaldo, who came within a whisker of breaking his five-game goal drought. Ronaldo twice hit the woodwork and saw another effort cleared off the line.
Another Brazilian striker, Mario Jardel, scored twice on Saturday to help Porto, the reigning Portuguese champions, to a 3-1 home win over Guimaraes. Porto, the only unbeaten team, led the table with 38 points, with Benfica, who beat Leca 5-1 away on Friday, in second place five points behind.
The two rivals meet next Saturday in a match that Benfica cannot afford to lose if the club is to retain any hopes of the title.