More than 3000 persons from the Mission Hill section of Roxbury marched on the State House yesterday morning, protesting what their leaders called "a conspiracy" between Harvard and the Massachusetts Department of Mental Health, in connection with a land-taking in the Mission Hill area.

Twenty-six buildings, homes for over 300 people, on Fenwood Road in Roxbury, between the Massachusetts Mental Health Center and the Peter Bent Brigham Hospital, are slated for demolition to make room for expansion of the Center.

Leaders of the march asserted that a large plot of land on the other side of the Center, purchased several years ago by the University from the Convent of the Good Shepherd, would be just as suitable for any adition to the Center.

The protesters charged that instead of taking the Harvard-owned land--which is largely vacant--the Mental Health Department is conspiring with Harvard to create a huge medical complex, at the expense of local residents.

Both Peter Bent Brigham and the Mental Health Center are affiliated with Harvard, and the Medical School is adjacent to the Brigham.

The demonstrators argued that expansion of the Center to the Fenwood Rd, site would complete an unbroken chain of Harvard owned or affiliated properties stretching more than a half mile from the Medical School to the old site of the Convent of the Good Shepherd.

L. Gard Wiggins, administrative vice-president, dismissed the charges yesterday as "untrue." He said there was "absolutely no collusion" between the University and the Department of Mental Health on the project.

"The land formerly owned by the Convent of the Good Shepherd is urgently needed for expansion of the Medical School," Wiggins stated. He added that the Convent land was "too far" from the Center to serve as an annex.

State Rep. William A. Carey (D-Roxbury), a spokesman for the marchers, said the "cursed and cancerous urban renewal program" was "driving human beings out of existence and destroying property at the expense of the taxpayers."

Carey attributed the land-taking to "creeping socialism which has grown to Communism," and said that there had been "altogether too much collusion" between Harvard and the Commissioner of Alental Health. "Our people are not swines." Carey added.

Harry G. Sullivan, State Mental Health Commissioner, rejected Carey's charge and explained that the land-taking was a "necessary development which has been in the planning for 10 years."

Most of the marchers were members of the Mission Church Parish, including 1000 from the Mission Hill parochial schools. They were led by Rev. Vincent Kelly, rector of the Mission Church.

The group formed at the Park St. subway station at about 10:30 a.m. yesterday and marched along the edge of the common to the State House. After climbing the main stairs of the State House, the group marched to the Governor's office in the building and demanded to speak with Governor's Peabody.

From there the demonstrators were herded to the Gardner Auditorium in the State House where they stayed until 1:30 p.m.