From the standpoint of transformational grammar, this experimental work evaluates the extent to which children choose or fail to generalize their rules for the placement of the negative particles "not" and "n't." The subjects were eight three- and four-year-olds of middle-class background who had been producing sentences with auxiliary verbs and negative particles at the time of the study and could easily imitate affirmative sentences with two auxiliary verbs. The children were instructed by their parents to imitate multiple auxiliary sentences with different placement of negative particles. The pattern of results showed that children consistently allowed "auxiliary verb+n't" only as the first auxiliary verb. While there was consistency within a given child as to placement of"not" as either first auxiliary or pre-predicate, there was no unanimity across the children. Significantly, it was found that three children failed in varying degrees to take advantage of the prospective generalization offered by negative sentences, and chose pre-predicate rather than first auxiliary placements of "not," even as they consistently imitated "auxiliary+n't" forms as the initial negative forms of multiple auxiliary sentences. (EJS)