Average faculty salaries rose substantially this academic year at most universities in the Washington area, as the pay of college professors nationwide had its largest real gain in 18 years, the American Association of University Professors reported yesterday.

Public universities generally recorded larger increases than private ones, both locally and across the nation, the report on the 1984-85 academic year said, as state tax revenues boomed because of the flourishing economy.

Pay raises at most private colleges also substantially outstripped inflation because of sizable increases in both tuition rates and federal student aid.

"In real terms, we're seeing more improvement than we have in a long, long time," said Maryse Eymonerie, the consultant who compiled the data for the AAUP. "Faculty earnings went down in the 1970s as inflation went up. Now that inflation is less, things are begining to be positive."

According to the report, average faculty salaries rose this year by 6.6 percent nationwide -- 2.5 percent above the rate of inflation. It was the fourth year in a row that salary boosts exceeded inflation, the report said, but these gains followed eight years in which faculty purchasing power fell because raises lagged behind the increase in prices.

The last year that average salary increases, when adjusted for inflation, were greater than now was 1967-68, Eymonerie said, when they came to 3 percent.

Locally, the largest increases this year were at Northern Virginia Community College and George Mason University, both more than 11 percent for continuing faculty. They were followed closely by the University of Virginia, American University and the University of Maryland, all of which reported average increases of more than 9 percent.

George Washington and Georgetown universities continued to have the highest average faculty salaries in the area, both about $38,000 for all faculty ranks. However, full professors at Georgetown earned the most, averaging $53,000.

Among public universities, the highest average salaries were at the University of Virginia at $36,400 -- about $2,100 more than the University of Maryland and $2,600 more than the University of the District of Columbia.

However, in a nationwide comparison of universities with similar programs, the University of Maryland moved from well below average in most faculty ranks to slightly above average. Virginia remained well above average. UDC, which is in a different category, continued to rank very high among comprehensive universities that do not have extensive Ph.D. programs.

Independent private universities, which include the Ivy League schools, have the nation's highest faculty salaries, followed by state-supported public universities. Private church-related schools generally pay the least.

Catholic University in Washington is part of this pattern, having among the lowest average salaries in the area -- $28,800 -- and falling in the bottom category nationwide for universities with extensive graduate programs.

The smallest gains locally were made by Montgomery College and Prince George's Community College -- both two-year institutions that had average pay increases of about 4 percent. However, with average salaries of more than $32,000, both schools continued to rank high compared with all community colleges nationwide.