The current popular case against the use of standardised ability tests in bilingual assessment is not as unequivocal as may be commonly assumed. Evidence currently available indicates that such tests generally measure the same constructs, with equal accuracy, regardless of language backgrounds. The purpose of this paper is to contribute to this debate by presenting a detailed comparison of the Illinois Test of Psycholinguistic Ability (ITPA) profiles of monolingual language-impaired children who have received the diagnosis 'specifically language-impaired' (SLI) (N = 95) and ITPA profiles of bilingual children who are referred for assessment of their language problems (N = 43). It is concluded that most bilingual children suffer from a 'knowledge-based' problem, while most monolingual children suffer from a more fundamental 'processing-based' problem. By presenting this analysis, we hope to contribute to the general debate about whether this commonly used test can be used in the assessment of bilingual children.