Fishermen, sharpen your hooks, bring out the cheese balls and grease your bicycles. Soon there's going to be trout fishing inside the Beltway.

No need to drive to the mountains of Virginia or the limestone streams of Pennsylvania for the thrill of a rainbow on the line. Potomac-Patuxent chapter of Trout Unlimited has convinced Maryland officials to stock the much-maligned Northwest Branch of the Anacostia with 3,000 trout.

The stocking area runs from Wheaton Regional Park South past Colesville Road, Columbia Pike, the Beltway, Riggs Road, University Boulevard and East-West Highway.

State cold water fisheries program director David Woronecki said the fish will be stocked during the weeks of March 13-April 3. The creel limit will be three per day and there will be no restrictions on lures and baits. A state fishing license and trout stamp are required, except for those under 16.

One offshoot of the program may be the restoration of respectability to the Northwest Branch.

Only the old-timers know the little river for what it once was and could be again.

Once the Northwest Branch had swimming holes from top to bottom. Before the war it was a country stream, and youngsters converged to its pools in the summer.

Jim Martin grew up in Four Corners and he recalls that until 1960 there was a good swimming on certain days.

"We once called up the Washington Suburban Sanitary Commission because sometimes the stream smelled and looked bad. One of the WSSC guys told me we could swim any day but Tuesdays and Fridays, because that's when they dumped the sewage in."

Whether it was sewage is unclear. But the rapid growth of suburban shpping centers and highways led to spilloff and silting in the stream and it lost its appeal.

Larry Miller and Frank Clark were among the crowd at Potomac-Patuxent Trout Unlimited that held out hope for the Northwest Branch.

Miller and Clark provided a guided walk along a piece of the branch last week. It had all the trappings of an abused resource. At Burnt Mills dam off Columbia Pike great clots of detergent foam built up at the base of the spillway. Trash lined the banks of the stream for 100 yards either side of the road.

But beyond that, the further in we trekked the more primitive and unspoiled the waters became. Below Columbia Pike it's like a mountain stream. The water runs fast and steady around huge boulders. The hillsides rise sharply from the stream bed.

And north of the Pike, above the dam, the Northwest Branch spreads out into a slow rolling meadow stream with broad, grassy banks ideal for casting to trout.

Said Miller, "The water quality has always been high enough; it's been a matter of getting it stocked. He said the Montgomery County Department of Enivronmental Health monitored the water and rated it good to excellent, sufficient to maintain trout like. And trout need high-quality waters.

Miller and Clark are hoping that a spinoff of the "put-and-take" stocking program will be development of what Clark calls a "residual holdover" - the bot water in the summer and begin reproducing.

According to Clark, "That's what trout that srvive the fishermen and happened in the Pain Branch after they stocked brown trout there 20 years ago." A tiny population of browns remains in the Pain Branch, although it's nowhere near sufficient to support sport fishing.

But for now they're pushing for many people to fish the stream. Miller said the state "wants a maxmium return. They figure it's a showcase and they want as many fish taken as possible."

Which could make it rough for Nick Orrick, one of the only two men known to have used the Northwest Branch for sporting purposes in recent years. Orrick and Chris Patterson, who lives in West Virginia, couldn't resist taking their chances in the spring of 1972, after storms swelled the stream to white water proportions.

They kayaked from Columbia Pike to Riggs Road, dodging boulders and fallen logs.

This year they'll have to dodge anglers, too. At least they'll have an audience.

Maryland officials listed these recommended spots for stocking the Northwest Branch: Bonifant Road, Randolph Road, New Hampshire Avenue, Riggs Road, University Boulevard. The fact they are recommended does not mean fish will be stocked at all or even any of these crossings, but if you see a state tank truck at one, grab your pole.

Clark said four spots along the branch that offer parking and easy access for fishermen are Adelphi Mills at Riggs Road, University Boulevard at the duck pond near the University of Maryland, Randolph Road in Wheaton between Georgia and New Hampshire Avenues, and Bonifant Road near the trolley museum.