CACI Inc. of Arlington reported a 73 percent drop in earnings for its latest quarter, posting a $174,608 profit (2 cents a share), down from the $658,377 (7 cents) earned for the same quarter a year ago.

Attributing the decline in profits to increased costs for bidding on government contracts and to the expansion of its market analysis division, the company said earnings for the first half of its fiscal year were down 61 percent from the previous year, to $471,833 (5 cents) from $1.2 million (13 cents).

Revenue for the latest quarter was down slightly to $24.3 million from $24.6 million a year ago. For the first six months of the year, revenue was down nearly 4 percent to $47.2 million from $49 million.Media General Inc., based in Richmond, also reported a drop in profits, its first in nine years.

Excluding nonrecurring charges, net earnings for 1985 were $33.4 million ($4.69), down nearly 10 percent from last year's $37 million ($5.21). Including nonrecurring charges, profits were $32.8 million, down 17 percent from last year's total of $39.8 million.

Media General attributed the decline to heavy price discounting in the newsprint industry, its restructuring of its broadcast services subsidiary and the costs of building Faifax County's cable system.

For the fourth quarter, net income was $9.3 million ($1.30), down from the $10.4 million ($1.47) earned during last year's fourth quarter.

Revenue for the quarter totaled $152 million, up from last year's $143 million. Dominion Bankshares Corp. of Richmond reported a 19 percent increase in earnings for 1985, making $39.3 million ($3.73) compared with $32.9 million ($3.25) in 1984.

Fourth-quarter profits of $11.1 million ($1.05) represented a 23 percent increase over the same quarter a year earlier when net earnings totaled $9 million.

Dominion's president and chief executive, Warner Dalhouse, attributed the increase to asset growth, an improvement in the net interest margin and the expansion of the non-interest revenue.