WHEN ROY WILKINS began his distinguished 45-year career with the NAACP, America was a different country - one where the American version of apartheid was sanctioned by political and police power; where there existed separate and unequal schools, neighborhoods, even drinking fountains; where blacks suffered blatant oppression in the South and a more subtle but still invidious oppression in the North. As he retires, Mr. Wilkins deserves to be honored as one of the civil-rights pioneers, black and white, who changed America into the country it is now.

It was a struggle, even after the landmark court rulings and civil-rights legislation. But Roy Wilkins, the most gentle and rational of men, always approached the task with dedication and an unshakeable faith. In his 22 years as executive director, the NAACP grew in membership, financial resources and influence, and it did the detail work that underlay much of the civil-rights movement's success. His contribution was incalculable.

In choosing Benjamin Hooks as its new executive director, the NAACP board shows it means to keep the organization in the vanguard of the quest for social justice in America. A lawyer and minister, Mr. Hooks is a former Federal Communications Commissioner and civil-rights leader in Memphis. Mr. Wilkins should have no doubt that his parting advice to the NAACP, "Be alert," will be heeded.

In part because of the successes of pioneers like Mr. Wilkins, the issues facing the organization and all of America - affirmative action and school desegregation that involves cross-town busing, for example - have become considerably more complex. And the views of black Americans about these issues have become more diverse. With the departure of Roy Wilkins, Mr. Hooks must rally the organization's membership and constituency to these new challenges. In this sense, the current St. Louis convention of the NAACP, as no other since its founding 68 years ago, marks the end of a great passage and the beginning of a new and demanding era.