This dissertation reviewed experimental studies centering on the Lovaas Method (LovM), reviewed experimental studies centering on Verbal Behavior Approach (VBA) and/or studies that focused on the primary verbal operants, and compared the effects of LovM and VBA on the development of tact repertoires of three 11 to 12-year-old students with moderate to severe mental retardation. We administered the ABLLS-short form, determined current levels of performance, and implemented the protocols in an alternative school for students with developmental disabilities. Specifically, 10 targets from two categories were taught receptively to mastery criterion and then expressively to mastery criterion using the LovM, and ten different targets from the same categories were trained using VBA, which included transfer trials across operants. A within-subject alternating treatments with baseline design was used to evaluate skill acquisition and identify an optimal practice in regards to frequency of target operants mastered to criterion, measures of efficiency, maintenance, and generalization. The results of this investigation suggest that both protocols are effective in teaching receptive and tact target operants; however, across all participants, VBA resulted in fewer errors and was more efficient in teaching tact operants. Limitations and recommendations for future research are discussed. [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.]