FOR FIVE YEARS Congress wrestled with immigration reform, finally passing legislation in 1986. The law, however, dealt with only half the picture, since it treated only illegal immigration. Now the unfinished portion of the reform is almost ready for Senate consideration. Next week, the Judiciary Committee is scheduled to take up a bill that restructures the system of legal immigration. Because it has the bipartisan support of the Senate's leading immigration experts -- Edward Kennedy and Alan Simpson -- little opposition is expected.

Here is the problem: under current law, certain immigrants -- spouses, minor children and parents of U.S. citizens -- are admitted without regard to their numbers. Other more distantly related relatives and those with professional or other skills in demand here are accorded preferences, but only 270,000 of these may enter each year. Because large numbers of extended family members apply, those who have important skills and professional qualifications, but no relatives here, receive only about 10 percent of the visas. In this category are many highly educated young people in Europe and the developing world who are effectively shut out in favor of a sister-in-law or nephew of someone already in this country.

The Kennedy-Simpson bill rearranges the preferences somewhat to encourage "new-seed," nonfamily immigration and increases the total number of visas available. The bill would continue the practice of admitting close family members without limit. Opportunities for more distant relatives, such as married brothers and sisters, would be limited. Married siblings have been a special problem because each comes with a spouse (and often children), who then creates preferences for his or her own family, thus using up a disproportionate share of the visas. The bill also creates a separate system for the skilled and educated so that they aren't competing with family members for entry. The end result will be a mix of 470,000 family members and 120,000 independent immigrants admitted each year. Refugees will continue to be admitted without reference to immigration limitations.

These reforms were recommended years ago by the independent Select Commission on Immigration and Refugee Policy, but action was postponed during the long legislative struggle on illegal immigration. The bill calls for a full review after three years -- particularly important in light of uncertainties about the effect on future immigration patterns of the ongoing amnesty program. The proposal is the result of much study and reflects compromises agreed to by thoughtful people. It should be passed.