Biotechnology companies are generating renewed interest on Wall Street and Capitol Hill as they produce new profits, products and policy questions.

Pharmaceutical, chemical and agricultural companies using new methods of genetic engineering will continue to be favored by investors during 1986, following an upswing fueled by the successes of a few companies in 1985, industry analysts said.

Biotech companies also expect Congress to continue debating the way federal agencies evaluate the new technology's products and possible risks.

Looking ahead, the industry hopes to build on the enthusiasm generated last year by new products that offer hope in the battle against cancer, by federal approval of a human drug produced through gene-splicing and by the rapid commercialization of tests to rid the blood supply of the AIDS virus.

Early last month, the National Cancer Institute found that interleukin-2, a protein produced by the body in minute amounts, shows promise as a cancer therapy. The news led to a temporary surge in the prices of biotech companies, such as Cetus Corp., Biogen N.V., Amgen and Immunex, which are working to produce the substance in commercial quantities through gene-splicing.

Similarly, Genentech Inc. received a boost early last year from promising results of studies on its genetically engineered blood clot-dissolving agent. In October, Genentech received federal approval of its genetically engineered human growth hormone, becoming the only source of the drug and the first biotech company to take a gene-spliced drug from laboratory to market.

The federal government also opened a biotech market worth millions last year when it approved the first commercial test to screen blood for antibodies to AIDS. This gave a boost to several companies specializing in the genetically engineered products called monoclonal antibodies, which are used in the tests. Two such companies received acquisition offers from large pharmaceutical companies last year, and others with product sales and profits may attract suitors this year.

Biotech stock prices increased 54 percent in the first 11 months of last year, according to Paine Webber's Biotechnology Index, based on 26 companies. That increase reflected a rebound from the 22 percent decline in 1984, said Linda I. Miller, an analyst at Paine Webber. The 1984 results had reflected investors' impatience with biotech companies that had yet to deliver long-promised earnings and products, which then emerged in 1985, she said.

Last year's spurt and bull market should pave the way for "continued good performance" this year, Miller said. "Biotechnology presents an opportunity for super growth."

Biotech companies also reaped benefits and costs last year from the government's efforts to clarify the regulatory picture. Companies hoping to apply biotechnology to agriculture were encouraged by the government's approval of outdoor field tests of plants and pesticides produced through gene-splicing.

But recent congressional hearings have revived concern about the government's ability and readiness to evaluate the environmental risks of releasing genetically altered living organisms. More hearings are planned for this year as the Senate considers legislation introduced last month that would strengthen the Environmental Protection Agency's authority over the outdoor and industrial uses of gene-splicing. Other biotech bills may be introduced in the House.

Some biotech industry experts said new legislation is unlikely to be passed. They predicted Congress would wait to see how existing regulations handle the new technology.

Many biotech companies are more concerned about export restrictions that could limit the industry's growth. They are worried that small companies will be forced to locate production facilities overseas or transfer technology to overseas partners. As a result, they are lobbying for legislation to relax export rules.