Data from elicited language tasks can add to the literature on the development of the complex syntax structures of embedded complement clauses in typically developing children. In the current study, preschool-age children (n = 27) participated in two elicited language tasks focusing on three types of embedded complement clauses: infinitival complement clauses in Task 1 and full propositional complement and WH-complement clauses in Task 2. Each task included the same 6 verbs, which were categorized as Mental State or Communication Verbs and High and Low Frequency Verbs. Participants were in one of three age groups (Two-Year-Olds: 2;10 to 3;0; Three-Year-Olds: 3;8 to 3;10; Four-Year-Olds: 4;6 to 4;8). Of interest were participant use of target verb with target structure in each task, as well as Frequency of complex syntax responses for each target verb, in order to examine development across age groups. Productivity with each verb was additionally of interest across group and task. Productivity was examined in relation to the selected verbs by Verb Category (Mental State of Communication Verb) and Verb Frequency (High or Low). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]