In the first 13 years after the federal government initiated support for family planning clinic services, there was a fivefold increase in the number of U.S. women obtaining these services from organized programs, from about 860,000 in 1968 to 4.6 million in 1981. This increase was due to the growth in the number of service providers and in the average number of clients served by each agency. Between 1968 and 1981, the number of provider agencies rose from about 1,400 separate agencies operating 1,800 clinics to 2,500 agencies administering 5,000 clinics. The average number of patients served by each agency increased from 600 to 1,800. Family planning clinics have continued to serve primarily low-income women; in 1981, four-fifths of the women served, or 3.7 million, had low incomes. In addition, an estimated 1.8 million low-income women obtained family planning services from private physicians. Thus, about 58 percent of the 9.5 million low-income women who were exposed to the risk of having an unintended pregnancy in 1981 made a contraceptive visit in that year; 39 percent went to clinics and 19 percent visited private physicians. Five million women 19 years of age or younger were at risk of unintended pregnancy in 1981; of these, 2.9 million (57 percent) obtained medically supervised family planning services--30 percent from organized programs and 27 percent from private physicians. Family planning clinic patients obtained contraceptive care from a variety of public and private health agencies in 1981.(ABSTRACT TRUNCATED AT 250 WORDS)