The 1998 Illinois High School Association (IHSA) State Championship Tournaments ended the twelfth State Championship Series conducted in Scholastic Bowl by the IHSA. It was the seventh season in which there were separate State Championship Tournaments held for small schools (Class A) and large schools (Class AA). For the second year, both Tournaments were held at the Peoria Civic Center.
Within each class, the state was divided into eight areas (Sectionals) Each sectional hosted a tournament, the winner of which advanced to the State Championship Tournament. The determination of these geographic boundaries was arbitrarily decided by the IHSA Office.
Each round was comprised of 30 toss-ups and accompanying bonus questions. The sectional tournaments and State Championship Tournament were all single elimination. Teams were randomly assigned to positions in the bracket without regard for record or performance.
The exception to the single elimination format occurred in the semifinals, where the two semifinal losers played a third place match. The top four teams earned trophies and medals for team members, coaches, principals, and activities directors. The trophies were of the design smaller than that of the athletic trophies given out by the IHSA.