Prepaid group practice as a concept for providing health care is now over 25 years old in the nation and in New York City. It has overcome initial opposition by the medical profession and has been adopted by government as a healthy strategy under the acronym HMO or "Health Maintenance Organization". The author asserts that on two major criteria for evaluating the health care system--accessibility to the health care system and cost of treatment--prepaid group practice compares most favorably with other types of Insurance plans. There are presently estimated to be 170 operational HMOs throughout the country providing service to some eight million enrollees. An additional 262 HMOs are in various stages of planning and development, although only 66 of these have the assistance of government funds for feasibility and planning surveys under the Federal HMO Act of 1973. The HMO is substantially an urban phenomenon requiring large concentrations of population and large initial sums of money. The HMO Act of 1973 was a Federal Law designed to promote and encourage the growth of prepaid group practice plans. Before and after the Act passed Congress, criticism began to develop and major problems began to emerge. The author advocates definitive and timely Congressional action to amend the Law in order to ensure its success. (Author/JM)