Among major issues facing the Maryland General Assembly during this 90-day legislative session:

Public Works -- Gov. William Donald Schaefer's proposal for a $290 million light rail system for the Baltimore area.

Math-Science High Schools -- A proposed public boarding school for 600 sophomores through seniors with unusual talents in math and science. The school would open in 1989 and cost an estimated $20 million to build.

AIDS -- Measures providing for mandatory testing for the virus, a central reporting system for persons with the disease and the distribution of free syringes to drug addicts to curb the sharing of contaminated needles.

Day Care -- A new loan program to help open new day care centers, and a $2 million increase in the state's subsidy of day care for poor children.

Mental Health -- Improvements in the quality of psychiatric treatment in Maryland that include reducing crowding in state psychiatric hospitals and increasing community-based services.

Physician Discipline -- Measures to strengthen the system for disciplining doctors in Maryland as part of a larger effort to bring down the cost of medical malpractice insurance premiums.

Economic Development -- A $20 million fund to help persuade businesses to move into Maryland or keep businesses from leaving.

Truck Safety -- Initiatives to double the number of roadside inspectors to increase routine and surprise checks and require owners to maintain trucks regularly.

Corporate Directors and Officers -- Legislation limiting the liability, after a vote of stockholders, of directors and officers of corporations in lawsuits by the corporation or its stockholders. Suits by third parties would be excluded under proposed legislation.

Port of Baltimore -- Plans to give more autonomy to the Maryland Port Administration by creating a new commission composed of six business executives that would oversee the port's operation.

Budget -- Schaefer has pledged to abide by the legislature's self-imposed spending limit calling for an 8.6 percent increase in the state's operating budget, despite a $271 million surplus.

Salaries -- Big raises have been proposed for the people on Schaefer's senior staff, including nearly $25,000 a year for some top aides, which legislators say would be difficult to justify when most state employees probably will get raises of about 4 percent.

Judges -- A bill that would eliminate contested elections for circuit court judges.

Prisons -- A comprehensive $330 million, 11-year plan to demolish antiquated prisons and build new facilities around the state, including a minimum-security prerelease center in Prince George's County.

Chesapeake Bay -- Environmentalists will be watching how much money Schaefer commits to the bay clean-up agreement by Maryland, Virginia, the District and Pennsylvania. There have been indications that it will be far less than the $15 million to $20 million conservation groups advocate.

Local Issues -- Montgomery County's top priority is financing for construction of a $6.6 million classroom building at Shady Grove for the University of Maryland's high-technology center.

Legislators from Prince George's will be seeking more money for the county's magnet school program and asking for authority to restrict charity gambling.

Anne Arundel legislators, in addition to pushing the light rail line, will be seeking funds to expand the county courthouse.

Howard County officials want approval of bills to allow the county to charge fees for weekend prisoners and to charge prisoners who have financial resources or insurance coverage for health care services. Howard legislators also are gearing up to fight passage of three bills dealing with the care and keeping of vicious dogs.