Purpose: A randomized controlled trial was conducted to compare the language and auditory processing outcomes of children assigned to receive the Fast ForWord Language intervention (FFW-L) with the outcomes of children assigned to nonspecific or specific language intervention comparison treatments that did not contain modified speech. Method: Two hundred sixteen children between the ages of 6 and 9 years with language impairments were randomly assigned to 1 of 4 conditions: (a) Fast ForWord Language (FFW-L), (b) academic enrichment (AE), (c) computer-assisted language intervention (CALI), or (d) individualized language intervention (ILI) provided by a speech-language pathologist. All children received 1 hr and 40 min of treatment, 5 days per week, for 6 weeks. Language and auditory processing measures were administered to the children by blinded examiners before treatment, immediately after treatment, 3 months after treatment, and 6 months after treatment. Results: The children in all 4 conditions improved significantly on a global language test and a test of backward masking. Children with poor backward masking scores who were randomized to the FFW-L condition did not present greater improvement on the language measures than children with poor backward masking scores who were randomized to the other 3 conditions. Effect sizes, analyses of standard error of measurement, and normalization percentages supported the clinical significance of the improvements on the Comprehensive Assessment of Spoken Language (E. Carrow-Woolfolk, 1999). There was a treatment effect for the Blending Words subtest of the Comprehensive Test of Phonological Processing (R. K. Wagner, J. K. Torgesen, & C. A. Rashotte, 1999). Participants in the FFW-L and CALI conditions earned higher phonological awareness scores than children in the ILI and AE conditions at the 6-month followup testing. Conclusion: Fast ForWord Language, the intervention that provided modified speech to address a hypothesized underlying auditory processing deficit, was not more effective at improving general language skills or temporal processing skills than a nonspecific comparison treatment (AE) or specific language intervention comparison treatments (CALI and ILI) that did not contain modified speech stimuli. These findings call into question the temporal processing hypothesis of language impairment and the hypothesized benefits of using acoustically modified speech to improve language skills. The finding that children in the 3 treatment conditions and the active comparison condition made clinically relevant gains on measures of language and temporal auditory processing informs our understanding of the variety of intervention activities that can facilitate development.