"You get only one chance to make a first impression"--an adage perhaps you've heard from a parent or teacher--applies to architecture as well as to people.

Whether at a home or hospital, a school or skyscraper, what you first see and feel when you enter a building can make a profound and lasting impression, one that may dominate all subsequent impressions.

Coming through a building's front door for the first time can be exciting or banal, inviting or off-putting. Spaces of arrival can be dark and intimate, or they can be expansive and filled with light. Entering the lobby or foyer may reveal immediately how a building is organized or, conversely, deny the visitor visual clues about what is to come.

Throughout history and across many cultures, architects and their clients have well understood the first-impression phenomenon. The sequence of movement and promenade toward and into a building, along with the spaces and surfaces "enclosing" the journey, have long been a primary concern of thoughtful architectural design.

Consider a few entry promenades and memorable arrival spaces here in the nation's capital: the Library of Congress; the White House; the Organization of American States building on 17th Street NW; the National Gallery of Art's East and West buildings on the Mall; the British Embassy, designed by Sir Edwin Lutyens, on Massachusetts Avenue NW; the National Cathedral; and the Willard Hotel.

Contrast these with the countless office buildings, apartment houses and individual homes whose entries are unremarkable and readily forgotten.

"Engaging" a building entails several functional and aesthetic phases of movement: walking through the nearby environment; traversing the courtyard, porch or colonnade in front of the entry; passing from exterior to interior; and arriving in the lobby.

The lobby space is critical. Here is where the visitor pauses to get oriented, or perhaps take off a coat or collapse an umbrella. This is the space most likely to set the architectural tone, the place where first impressions coalesce.

Regrettably, the first encounter with many buildings, especially everyday commercial and governmental buildings, is through often unwelcoming arrival spaces that are drab, awkwardly configured and inhospitable. Entrance plazas can be dreary, wind-swept spaces devoid of life. Lobbies may be little more than fattened corridors filled with an excess of objects and information.

Sometimes the first experience upon arrival in a building is getting through the security checkpoint, typically an ensemble of armed guards, conveyor belts and metal detectors.

Recognizing that perceptions matter, the nation's biggest real estate owner and manager, the General Services Administration, has embarked on an ambitious long-term campaign to enhance the architectural quality of entrances, lobbies and interconnected public spaces--the promenade from curb to front door and lobby, then from lobby to elevators and corridors--in thousands of existing federal buildings throughout the United States.

The GSA has appropriately named this initiative "First Impressions."

Spearheaded by Robert Peck, the GSA's commissioner of public buildings, and guided by the GSA's design strategy consultant, Gensler & Associates, First Impressions seeks to create public spaces that are orderly and attractive in federal edifices.

Several actions have been highlighted by the GSA and Gensler as necessary to achieve favorable first impressions.

* Reducing clutter by ensuring that miscellaneous signs, posters, messages and bulletin boards, furniture, recycling bins and other furnishings are not scattered around haphazardly.

* Unifying and simplifying signs, based on a comprehensive prototype, to provide graphically clear and consistent information within government buildings.

* Relegating the automated teller machines and vending machines currently congesting building entries to designated areas peripheral to or completely outside entrance lobbies.

* Streamlining security by using the most advanced, compact technology integrated into lobby spaces as unobtrusively as possible.

The ultimate objective of the GSA is to transform the image of federal buildings.

The task is daunting. Each building in the GSA inventory across the country must be thoroughly assessed for aesthetic as well as functional and technical deficiencies. Most buildings will require only retrofitting. In older or obsolete structures, upgrading public spaces will be part of rehabilitating the entire building. Hundreds of historically significant federal buildings will demand especially sensitive redesign and upgrading.

Remediation priorities must be established to rank both buildings and specific improvements for each building. The GSA's chief architect, Edward Feiner, estimates that about 200 federal buildings will be highest on the list.

The costs will be funded from GSA's annual repair and alterations budget.

Although Gensler has prepared overall architectural goals for the program, local firms within regions will design improvements for each site based on specific building type, building conditions and regional context.

Eventually, much more than entrance lobbies must be rethought. Consider the many elements outside that contribute to first impressions before visitors ever set foot inside: landscaping of plazas; approach walkways, stairs and ramps; railings; porches and canopies; lobby doors and windows; exterior lighting and signs; and outdoor furniture.

Many of the First Impressions enhancements contemplated by the GSA are cosmetic. Yet if executed with imagination and skill, they can turn otherwise dull or disorganized spaces into places that the public and federal workers will enjoy passing through--and remembering.

Indeed, if the program is successful, you may enter a federal building a few years from now and, feeling especially welcome, think that GSA stands for "Great Sense of Arrival."

Roger Lewis is a practicing architect and a professor of architecture at the University of Maryland.