URBANA – More than 500 people marched in the rain Monday morning in the first-ever strike by University of Illinois graduate students.

Not all were members of the Graduate Employees' Organization, which has about 2,700 members. Many were undergraduates and faculty, the GEO said.

Among them was a University of Michigan grad student, Matt Desan, who drove down from Ann Arbor with four others in support of the union's demand for tuition-waiver guarantees.

"They've been part of Michigan's contract (for its union, also called the GEO) since 1987," he said.

On the first day of its strike, the GEO was concentrating on four buildings: Davenport Hall, the English Building, Gregory Hall and the Foreign Language Building. GEO spokesman Peter Campbell said strikers and supporters would stay out of those halls "24-7" until further notice.

UI spokeswoman Robin Kaler said the strike was not causing undue problems for the Urbana campus.

"We're finding that most classes are still in session," she said, although, she added, there have been complaints from students about noisemakers used on the picket line.

Kaler said "some of the professors have requested alternate locations, and some are combining sections."

The UI contends the union by striking is rejecting offers of increases to the minimum stipend for 50 percent appointments (20 hour a week, nine months a year) of $13,840 (year one, increased from current minimum of $13,430, retroactive to August 2009); $14,250 (year two); and $14,820 (year three).

The UI offers also includes increases to the student health insurance fee subsidy of 65 percent (year one, increased from the current 50 percent subsidy); 75 percent (year two); and 75 percent (year three).

The main disagreement, Campbell said, was over tuition waivers. The UI Board of Trustees' rules only protect in-state tuition waivers, he said, and the proposal would provide no protection for waivers if the administration moved to change some or all out-of-state waivers to in-state tuition.