Abstract Bilingual children are often misdiagnosed as having a speech disorder when they truly exhibit normal development. In addition, speech-language pathologists (SLP) are avoiding the assessment of bilingual children due to the lack of knowledge and resources necessary for best practice with this population. Misdiagnosis of speech sound disorders in this population has long-term emotional, financial, and educational costs. Misdiagnosis of speech disorders in bilingual children can be prevented if we acquire more information on what constitutes normal and disordered speech development in the bilingual population. The current research is designed to validate a model of speech sound production in bilinguals to frame a screening tool for Latino preschoolers. Due to differences in speech production found in bilingual preschoolers (Fabiano-Smith & Goldstein, 2010a; 2010b; Fabiano-Smith & Barlow, 2010), an assessment procedure that evaluates the speech of bilingual preschoolers that takes into account both English and Spanish is necessary to prevent misdiagnosis of speech sound disorders. The Specific Aims of the proposed research are to (1) to validate our model of speech sound production in bilinguals, the PRIMIR 2 model and (2) to improve the existing version of the assessment procedure utilized in Phase 1 of our research using Item Response and Classical Test Theory approaches to reliability. Bilingual children with typical and disordered development will be compared to their English-speaking peers on measures of speech sound ability. Children will produce sounds in single words and their productions will be phonetically transcribed. Child productions will be examined, in both English and Spanish and across both languages, on common diagnostic measures used for monolingual children. Mixed effects regression models will be used to identify between-language interaction in bilingual speech and the Receiver Operating Characteristic Curve (ROC) will be used to determine sensitivity and specificity of the diagnostic measures examined. Item Response Theory (IRT) will be used to identify a set of test items that are sensitive and specific to bilingual children with suspected speech sound disorders. Findings will lead to a characterization of typical and disordered speech sound development in bilingual children and diagnostic guidelines for speech-language pathologists to use in the differential diagnosis of speech difference from speech disorder. These findings will reduce diagnostic error in the identification of speech sound disorders in this population, reducing health disparities for Latino children.