This investigation studied the development of the form and function of negative sentences, and how it relates to the input on negation that children receive from their parents. The data came from three children: two from a previous study (Bellugi) and one the son of the investigators. A detailed analysis was carried out of the syntactic form and semantic function of all clearly interpretable multi-word negatives in the children's speech and in the parents' speech for the first five samples. Analysis of the forms and functions of the negative sentences of the three children, up to a mean length of utternace of 2.6, and of their parents, concentrated on rejection and denial negatives. The results revealed clear differences in the use of negatives by the parents that are reflected in the speech of their children. It is concluded that the results of this study provide little evidence for the idea that the use of NEG+S negatives, that is a negative marker outside the kernel sentence, represents a general stage in the acquisition of negation. The pattern of mastery of negation reflects both the predominant functions to which the child puts the negative and the frequency of different forms and functions in the parental speech. (AMH)