Children with selective mutism (SM) display a failure to speak in select situations despite speaking when comfortable. The purpose of this study was to obtain valid assessments of receptive and expressive language in 33 children (ages 5 to 12) with SM. Because some children with SM will speak to parents but not a professional, another purpose was to explore the efficacy of employing parents to deliver test stimuli. Parents received training on presenting standardized test material and were monitored during testing by a professional who scored and interpreted the results. Professional-administered tests underestimated children's capabilities. However, even with parents, children's scores decreased as the tasks changed from receptive to expressive vocabulary and from narrative comprehension to telling a story on their own. Thus, although SM is typically classified as an anxiety disorder, an underlying expressive narrative language deficit was identified in 42% of children with SM using this new procedure. (Contains 3 tables and 2 figures.)