The familial transmission of speech and language disorders was investigated using a community sample of five year old children with speech and/or language impairment and a control group with normal language skills. The results indicated a significantly higher prevalence rate of language-related problems in families of speech and language impaired children than in normal language controls. Girls with speech/language impairments had more affected relatives than boys, suggesting that girls with this type of family history are at a greater risk of developing speech or language related problems. The pattern of transmission of speech and language disorders was also compared with published reports of the family histories of stuttering and reading disabilities, and with reports of cognitive and linguistic deficits among families of autistic individuals. The findings are discussed in relation to the theory of an underlying neurolinguistic diathesis common to these various disabilities.