DSM-IV: Phonological Disorder

Diagnostic criteria for 315.39 Phonological Disorder
(cautionary statement)  

A. Failure to use developmentally expected speech sounds that are appropriate for age and dialect (e.g., errors in sound production, use, representation, or organization such as, but not limited to, substitutions of one sound for another [use of /t/ for target /k/ sound] or omissions of sounds such as final consonants). 
B. The difficulties in speech sound production interfere with academic or occupational achievement or with social communication. 
C. If Mental Retardation, a speech-motor or sensory deficit, or environmental deprivation is present, the speech difficulties are in excess of those usually associated with these problems. 

Coding note: If a speech-motor or sensory deficit or a neurological condition is present, code the condition on Axis III.

Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, fourth Edition. Copyright 1994 American Psychiatric Association