Background: High levels of behaviour problems are found in children with language impairments, but less is known about the level and nature of language impairment in children with severe behavioural problems. In particular, previous data suggest that at primary age, receptive impairments are more closely related to behaviour problems, whereas expressive language has a closer link at a later age. Aims: The study assessed expressive and receptive language problems in boys excluded from primary and secondary schools, to investigate the extent of impairment, the pattern of relations between age, receptive and expressive language, and relations with different aspects of behaviour. Sample: Nineteen boys (8 ? 16 years of age) who had been excluded from school and 19 nonexcluded controls matched for age and school participated. Method: The sample was given assessments of: receptive language from the British Picture Vocabulary Scale (BPVS), and Wechsler Objective Language Dimensions (WOLD); expressive-language evaluations from the Wechsler Intelligence Scale for Children (WISC); auditory working memory evaluations from the Clinical Evaluation of Language Fundamentals (CELF); verbal reasoning (from the WISC); and non-verbal IQ assessments Raven's matrices. Teachers completed behaviour ratings using the Strengths and Difficulties Questionnaire (SDQ). Results: Excluded boys were significantly poorer than controls on expressive measures but similar on receptive language and non-verbal IQ. Boys excluded from primary school were poorer than controls on auditory working memory. Expressive problems were linked with high levels of emotional symptoms. Conclusion: Many of the excluded boys had previously unidentified language problems, supporting the need for early recognition and assessment of language in boys with behaviour problems. Expressive problems in particular may be a risk factor.