Children with speech sound disorders (SSD) have difficulty producing, using, and integrating the sounds of their target language system. In addition, some children with SSD have difficulty perceiving and categorizing speech sounds into separate sound categories suggesting that their auditory sensory responses may also be impaired. While children with SSD are traditionally thought to be unable to detect subtle differences between sounds, there is little or no understanding of the underlying perceptual mechanisms implicated in SSD. Based on our own work and that that of existing evidence, we suggest that children with SSD may have difficulty creating phonological representations due to their inaccurate perception of speech sounds, which then directly affects their ability to produce speech sounds correctly. Since the incidence of SSD is relatively high (5-8%), a good understanding of the underlying nature of the disorder could improve the lives of many children and their families by informing clinical management of the disorder. Thus, assessment and treatment could target all areas of deficiency, including speech production and speech perception. We propose to address this important issue by using electrophysiological measures (event-related potentials, ERPs) to assess auditory sensory response measures in children with SSD and their age-matched typically developing (TD) peers. This will allow for a better understanding of the underlying neural mechanisms associated with the development of speech sound production. If children with SSD have atypical speech sound encoding and discrimination deficits, their ERP responses will differ from the outcomes of TD children. Moreover, changes in the auditory sensory responses of the children with SSD that occur in conjunction with two different speech treatment approaches (one with and one without speech perception training) will be assessed; this will allow for a better understanding of how the neural mechanisms associated with SSD change over time. It is predicted that the speech treatment program that includes perceptual training will enhance the phonological representations of children with SSD above and beyond what occurs with traditional speech treatment alone, resulting in ERP amplitude and latency waveform changes. This research program is significant because accurate speech perception affects speech sound production, as well as academic skills such as reading and spelling. Thus, having poor speech perception impacts children's overall ability to effectively communicate and learn. This study is innovative due to its use of ERPs to identify the typical and/or atypical neural response patterns underlying the perception of speech sounds in children with SSD. In addition, changes in the ERP waveforms that occur after a period of speech treatment could be indicative of improved speech perception abilities and effective treatment techniques, resulting in more specified phonological representations. Identifying whether abnormal auditory sensory processing is present in children with SSD will significantly impact how the disorder is assessed, characterized, and treated.