American Management Systems Inc., the Arlington-based computer systems and professional-services company, said its profit rose 45 percent in 1987, to $7.6 million (73 cents) from $5.2 million (51 cents) a year ago. Revenue rose 29 percent, to $174.3 million from $135.5 million.

In the fourth quarter, AMS earned $3.3 million (32 cents), nearly double the $1.7 million (17 cents) it earned a year ago. Revenue rose 33 percent in the quarter, to $45.1 million from $34 million.

Washington Homes Inc., the Waldorf-based home builder, said its profit dipped 21 percent in its second quarter ended Dec. 31, to $1.8 million (31 cents) from $2.2 million (39 cents). Revenue slipped 6 percent, to $17.8 million from $18.8 million.

For the first half, the company said it earned $4.4 million (78 cents), up 10 percent from $4 million (76 cents) a year ago. Revenue rose 16 percent in the half, to $42.1 million from $36.3 million.

Comnet Corp., a Washington-based technology and health care company, said it earned $519,000 (20 cents) in the third quarter ended Dec. 31, up two-thirds from $303,000 (12 cents) a year ago. Revenue rose 11 percent, to $11.3 million from $10.2 million.

For the first nine months of its fiscal year, Comnet earned $1.4 million (53 cents), twice the $694,000 (28 cents) it earned a year ago. Revenue rose 11 percent, to $32.7 million from $29.5 million.

Tempest Technologies Inc., a Herndon-based computer equipment company, said it earned $1.3 million (16 cents) in the third quarter ended Dec. 31, up 32 percent from $974,000 (14 cents) a year ago. Revenue rose 3 percent in the quarter, to $7.4 million from $7.1 million.

For the first nine months of its fiscal year, Tempest earned $3.4 million (47 cents), twice the $1.7 million (24 cents), it earned a year earlier. Revenue for the nine months rose 52 percent, to $20.4 million from $13.4 million a year earlier.