The national debate on health-care reform has highlighted a fundamental flaw in our medical system - the lack of doctors, even for those who have insurance, in rural and inner-city areas.

There is only one practical way to deliver medical care to the tens of millions of Americans who lack it: mandatory public service by physicians.At the end of 1992, an estimated 3,700 non-specialist physicians were needed in medically underserved areas. Although many physicians provide care to the needy at a reduced fee or no charge, volunteer efforts, splendid as they are, will never reach all Americans isolated by poverty, geography or residence in inadequate nursing homes, prisons or mental institutions.

While these citizens receive care for serious illnesses requiring hospitalization, they remain deprived of basic health care.

Previous solutions have proved woefully inadequate. For example, community health centers today treat 6 million patients - only a small portion of the 35 million with no health insurance and an even smaller fraction of others who might also benefit from the care such centers provide.

Other insufficient solutions have included expanding the enrollment in health insurance plans, aggressive recruitment of physicians to underserved areas and educating patients to use medical care early and wisely when ill.

Unfortunately, training more physicians will only exacerbate the uneven distribution of doctors. Physicians tend to practice in the affluent communities where they like to live and close to the latest technologies required to practice a specialty.

Another cause for regional shortages is that many young physicians graduate from medical school with a large tuition debt that often influences their choice of what and where to practice.

Mandatory public service for all physicians is not a radical idea. Beginning with World War II and continuing into the 1970s, physicians were required by law to serve for two years in the armed services or Public Health Service when called. They gave medical care to patients in military installations and publicly owned hospitals, to native Americans and to inmates of Federal prisons.

Mandatory service for physicians would also provide lessons for doctors now unavailable in medical school curriculums. Young physicians could not help but gain a deepened awareness of devilishly difficult "nonmedical" problems such as drug and alcohol addiction, family violence and teenage pregnancy that affect the health of patients.

A sense of obligation and social service once was a tenet of a physician's medical training and practice. Mandatory service needs to be reintroduced and re-emphasized for the entire profession. Medicine, the physician and, most importantly, the patient would be better served.