One in every four federal workers is enrolled in a health maintenance organization rather than the more traditional fee-for-service kind of health insurance plan. Many more are expected to switch to HMOs during the insurance open season that starts Nov. 13.

People pick HMOs because many offer low premiums compared with traditional health plans. HMOs also emphasize preventive medicine, have minimal paperwork and require subscribers to pay little or nothing for most medical services. They also offer a prearranged group of doctors to choose from, something that can be helpful to people new to an area.

HMOs also have their downside: Most offer a limited number of doctors. Doctors sometimes drop their affiliation with HMOs, leaving patients to find a new physician within that HMO family. Also, many people complain about long waits for appointments through HMOs. And some people feel they get less respect and service as an HMO patient, and they don't like the physician referral process in many HMOs.

During the health insurance hunting season, federal workers and retirees must pick their 1991 health plan. Locally about 25 standard fee-for-service plans are available. None of the plans can refuse anyone, or bar a person because of a pre-existing medical condition.

Last week we printed the new premium rates for those fee-for-service plans. Today we are listing the 1991 premiums that HMOs will charge federal workers and retirees. Retirees will pay the same premiums but on a monthly basis.

Premiums on average will go up 5.4 percent next year. Some of the HMOs will go up more than that. But many are still much better bargains than regular plans. Here are the 1991 biweekly premiums:

CapitalCare: Single, $29.10, up $3.45; family, $90.93, up $10.67.

Group Health Association of DC: High option single (self-only) premium will be $23.07, an increase of $2.39; high family premium, $68.06, up $9.77; standard single option, $12.89, up $1.19; standard family, $33.17, up $3.34.

Kaiser: Single plan, $15.56, up $1.29; family, $39.98, up $3.44.

Lincoln National Plan: Single plan, $19.37, up $3.25; family, $64.04, up $18.62.

PruCare: Single, $26.13, up $1.02; family, $73.99, down $9.07.

CAREFIRST, Maryland: Single, $15.48, up 40 cents; family $41.03, down $6.34.

Chesapeake Plan: Single, $15.21, up 98 cents; family, $40.84, up 53 cents.

Columbia: Single, $17.19, up 92 cents; family, $63.31, down $3.15.

Free State: Single, $17.12, up $1.46; family, $62.52, up $2.78.

HealthPlus: Single high option, $16.44, up $1.19; family high, $37.81, up $2.91; single standard, $12.87, up $1.19; standard family, $29.60, up $2.91.

Johns Hopkins: Single, $15.11, up $1.46; family, $40.88, up $3.98.

MD-IPA Plan: Single, $12.86, up 98 cents; family, $36.33, up $2.76.

Potomac Plan: Single, $18.43, up $1.01; family, $65.93, down $2.73.