It's a shame that the person elected to replace Frank Medico as the delegate from the Mount Vernon area has been such a failure in Richmond {"Last Place Is Fine by Fill," Virginia Weekly, Jan. 17}. Gerald A. "Jerry" Fill (R) was recently awarded the honor of "least effective member," of the Virginia House of Delegates. It's even more of a shame that Mr. Fill says he is proud of the "honor." With Virginia facing such a serious budget shortfall, we need a strong voice who can work with all members, regardless of party, to protect the interests of the people in Northern Virginia. It is obvious that Jerry Fill is not that person. We expect better. SHIRLEY B. BOLSTAD Alexandria

Donald P. Baker writes that Del. Gerald A. Fill is not embarrassed by having finished last in the effectiveness poll.

Careful analysis of the article shows that a low rating is to be expected for a first-term Republican legislator. Del. Fill's rating was depressed by conditions beyond his control: (1) Only Democrats voted, and Del. Fill is a Republican. Practically all the Republican legislators received fewer votes than Democrats. (2) As Del. Fill won his election with only a small margin of votes, he is a natural target for the Democrats to eliminate in the next election. (3) The legislators with the most years in the legislature placed higher on the list. Del. Fill is a first-year delegate. (4) Del. Fill disregards limitations placed on him by seniority, Southsiders, "good old boys," lobbyists and vote traders. This independence has made him dangerous to the existing power structure.

On the other hand, Del. Fill has acted independently in filing bills and in soliciting support for them. Of interest especially to Northern Virginians were his bills to place a 5 percent cap on increasing property taxes and a bill to repeal the legislature's authority to hold a referendum to increase state income taxes by 17 percent.

My point is that Del. Fill has been taking his responsibilities seriously and has been conducting his business in the legislature the way we voters feel it should be conducted, despite how Democratic legislators may vote on his "effectiveness" rating. OSGOOD TOWER Annandale