Joanne Lagatta, 13, of Clinton, Wis., knew she had the 1991 National Spelling Bee sewed up when she was given the word "antipyretic."

But it had taken more than 18 rounds of stiff competition against Maria Roshini Mathew, 11, a sixth-grader from Sterling, Ill.The two girls started their see-saw battle of words in the eighth round when Eric Herman, 12, Hights-town, N.J., misspelled "tetrastoon."

When only two spellers remain, the rule of miss-and-out changes. The winner must spell two consecutive words correctly.

Words such as "antepirrhema," "oolemma," "marcescence" and "gabarit" spelled a miss for each girl.

When each misspelled a word, a new "round" of words began.

Occasionally, a word was spelled correctly, but when the second and deciding word was given, it was misspelled.

In round 26, Lagatta correctly spelled "inappetence," a medical term describing a patient's lack of appetite. But the contest wasn't over. Again, she had to spell a second word.

When she heard the pronouncer give the word, which meant "preventing, removing or allaying fever," a smile came across her face.

Slowly she spelled the word that declared her the champion: "antipyretic."

What is the secret for her spelling talent? "Whenever I see a new word, I study it."

It paid off for the Clintonville Junior High School student. She receives a check for $5,000 along with a trophy and other prizes. She was scheduled to appear on television talk shows Friday morning.

As second-place winner, Mathew receives $4,000.

All spellers will be honored at an awards banquet Friday evening in the Capital Hilton ballroom.