Children's use of conjunctions was examined for linguistic complexity, developmental differences, and ethnic differences. Third, sixth, and ninth grade Anglo-American, Black, and Hispanic students completed sentence fragments ending in "and,""but,""because," and "even though." These conjunctions can be paired "and-but" and "because-even though," thereby making the second member of each pair the negative of the first. The positive member of each pair proved to be easier to master than the negative one, with the overall order of difficulty (from easiest to hardest) being because-and-but-even though. This order of difficulty was constant across grades and ethnic groups. All ethnic groups showed improvement in the use of conjunctions between third and ninth grades; but Anglo-American students achieved effective mastery of each conjunction earliest, while Hispanic students achieved mastery latest. (Author/RL)