This paper presents a model of syntax acquisition, whose main points are as follows: Syntax is acquired in an item-based manner; early learning facilitates subsequent learning--as evidenced by the accelerating rate of new verbs entering a given structure; and mastery of syntactic knowledge is typically achieved through practice--as evidenced by intensive use and common word order errors--and this slows down learning during the early stages of acquiring a structure. The facilitation and practice hypotheses were tested on naturalistic production samples of six Hebrew-acquiring children ranging from ages 1;1 to 2;7 (average ages 1;6 to 2;4 months). Results show that most structures did in fact accelerate; the notion of "practice" is supported by the inverse correlation found between number of verbs and number of errors in the earliest productions in a given structure; and the absence of acceleration in a minority of the structures is due to the fact that they involve relatively less practice. (Contains 1 footnote.) [This research was supported by a Marie-Curie Intra-European Fellowship, the Israel Foundations Trustees, the Martin and Vivian Levin Center for the Normal and Psychopathological Development of the Child and Adolescent, the Sturman Center for Human Development, and the Levi Eshkol Institute for Economic, Social, and Political Research.]