New food stamp eligibility guidelines, scheduled to go into effect today, will bump an undermined number of District residents from the program, including many working poor and elderly persons on Fixed incomes.

At the same time, city officials said, the new guidelines and expanded administrative efforts are expected to bring into the program thousands of poor people who either did not previously qualify for food stamps or did not apply.

While no specific gain and loss figures were immediately available from city officials, the U.S. Department of Agriculture predicted that as many as 3 million people would be added to the national food stamp rolls while just as many would become ineligible.

The previous eligibility system allowed households to use multiple deductions, including medical, child care and high shelter costs, to reduce incomes to an eligible level.

The new guidelines permit only three standardized deductions: a standard $65 deduction; 20 per cent of a household's gross earned income, and a maximum $80 deduction to cover child care and shelter costs. No medical deductions are allowed.

Cheryl Fish, a counselor with the District's Legal Counsel for the Elderly office, said the loss of the medical deduction will exclude many elderly people on fixed incomes, with high medical costs, from the program.

Working poor people, especially single parents with high child care and shelter costs, may also be excluded, said Jane Morrison, a metropolitan area food stamp official.

Ironically, in January the U.S. Department of Agriculture eliminated the food stamp purchase requirement to help-provide food stamps to the eligible elderly and working poor people unable to pay even small food stamp fees.

Now namy of these same people who joined the program in January may become ineligible to receive food stamps within the next 120 days.

Between March 1 and July 1, all states are required to use the new rules to review the eligibility of all food stamp recipients. Persons who become ineligible will be given at least 10 days notice, said Sharon Ruby, a USDA outreach officer. Persons whose food stamp allotments are reduced or increased under the new program will receive notice of the adjustments during the 120-day period.

In the District, the changes are expected to have a positive effect, adding nearly 4,000 households to the program, said William Gray, acting bureau chief of the welfare division that determines food stamp eligibility.

Alice Ricci, staff assistant to the administrator of the Payments Assistance Administration, said more than 40,000 households (or about 106,000 people) are presently certified as eligible to receive food stamps. About 33,000 households, (or more than 88,000 people) actually receive the stamps during any given month, she said.

City officials were unable to predict how many eligible people the new program would bump.

Ruby, said two major changes now make the stamps more accessible to persons unable to get them before. These changes make the stamps free of charge and allow eligible households without access to cooking facilities to now receive food stamps.

According to Ruby, the guidelines also reduce the maximum income levels allowed. To receive food stamps, a single person cannot have a net income greater than $277 a month. A family of two is limited to an income of $365 a month; a family of three, $454 a month, and a family of four, $542 a month.

In addition, a family that owns a car with a fair market value of more than $4,500 is ineligible for the program unless the vae ehicle is used by a person who is self-employed.

Ruby said college students receiving food stamps will have to work 20 hours a week to remain in the program.

Along with the changes expected to trim higher income people from food stamp rolls, there are several changes the USDA expects will help bring more poor people into the program. Among those changes:

Eligible households must now receive food stamps within 30 days after they apply, with benefits retroactive to the date of application. Previously, food stamp benefits began the day eligibility was determined, according to the USDA.

People receiving welfare, unemployment and Supplemental Security Income must be informed about the food stamp program. Many of these people were unaware of their eligibility before, the guidelines said.

Training must be provided for food stamp workers and some localities must also train bilingual workers. No training standards were established before.

Households no longer need access to cooking facilities to qualify for the program.

The changes are among several major revisions made in the program by the Food Stamp Act of 1977.

The USDA guidelines for the new food stamp program say the goal is to simplify the program and the discourage fraud. It is further expected to reduce administrative costs, simplify the application process and end the mismangement of funds that resulted from the handling of cash when the purchase requirement was in effects, the guidelines say.

USDA has requested a $6.2 billion budget to implement the program.