Two hypotheses related to the emergence of multiword speech were explored: (1) that multiword speech follows developments in children's ability to map communicative intents to single-word expressions; and (2) that the acquisition of these mapping principles paves the way for the emergence of syntax. The developments consist of an increase in the use of multiple realization rules for the same intent and an increase in the use of variable-type, selective realization rules. Sixteen 12- to 28-month-old children were videotaped six times in a year. The emergence of syntax was found to follow by 0-6 months a steep increase in the use of multiple mapping rules for the realization of the same intents in one-word utterances, as well as an "explosion" in the use of variable-type mapping rules. The results raise the possibility that an understanding of the componential structure of communicative intents, and of the ways selected components may be mapped to expressions, is a necessary antecedent to understanding the mastery of patterned speech. (Author/SH)