American Capital and Research Corp., a Fairfax environmental services firm that has grown rapidly in recent years through acquisitions, yesterday reported rapid growth in earnings as well -- a 64 percent rise in its fiscal first quarter.

The company earned $2.8 million (15 cents a share) in the first quarter ended May 31, compared with $1.7 million (12 cents) in the first quarter last year.

ACR also reported revenue of $132 million in the quarter, 22 percent higher than the $108.5 million a year earlier. A spokeswoman said roughly 35 percent of the growth in revenue and earnings came from acquisitions.

ACR Chairman James O. Edwards has led the company through a rapid-fire series of acquisitions, buying 13 companies in the past three years, including the nationally prominent but financially troubled Kaiser Engineers of Oakland, Calif.

The acquisitions fueled ACR's impressive growth. Its revenue rose from $57 million in fiscal 1987 to $297 million in fiscal 1989 to $500 million in fiscal 1990, ended Feb. 28. In December, ACR sold stock to the public to help pay off some of its debt and finance further acquisitions.

About 50 percent of the engineering and environmental services company's sales come from the federal government, another 15 percent from state and local governments and the rest from private corporations and foreign governments.

While other local professional services companies have said federal budget cuts and an economic slowdown have recently cut into their sales, ACR has won several major contracts in the past three months.

Those include a $119 million construction management contract for the Boston Harbor cleanup, a $50 million environmental engineering contract with the Air Force, a $31 million engineering and construction management contract with a major steel company, a $13 million subcontract to help develop an automated system for the U.S. Patent and Trademark Office and several multimillion-dollar contracts to provide consulting services to the Environmental Protection Agency.

ACR said its backlog of work exceeds $1 billion.

Group 1 Software Inc., a Greenbelt-based company that supplies computer software to the direct marketing industry and other volume mailers, reported gains in revenue and earnings in the fiscal year ended March 31.

The company earned $2.95 million (70 cents) in the year, up 7 percent from $2.76 million (66 cents) the previous year. Revenue rose 14 percent, to $20.3 million from $17.7 million.

Fourth-quarter profits increased 20 percent to 1.2 million from $1 million in the comparable period in 1989. Revenue rose 18 percent, to $6.75 million from $5.7 million in the same period a year ago.

Staff writer Willie Schatz contributed to this report.