In 2016/17, the CATALISE Consortium published the results of a multinational and multidisciplinary Delphi consensus study, representing agreement among professionals about the definition and process of identification of children with Developmental Language Disorder (DLD) (Bishop etal., 2016, 2017). The extent to which the current clinical practice of UK speech and language therapists (SLTs) reflects the CATALISE consensus statements is unknown. To investigate how UK SLTs' expressive language assessment practices reflect the CATALISE documents' emphasis on the functional impairment and impact caused by DLD, by examining: whether multiple sources of assessment information are gathered; how standardised and non-standardised sources are combined in clinical decision-making, and how clinical observation and language sample analysis are utilised. An anonymous, online survey was carried out between August 2019 and January 2020. It was open to UK-based paediatric SLTs who assess children up to age 12 with unexplained difficulties using language. Questions probed different aspects of expressive language assessment which are referred to in the CATALISE consensus statements and supplementary comments, and asked about participants' familiarity with the CATALISE statements. Responses were analysed using simple descriptive statistics and content analysis. The questionnaire was completed by 104 participants, from all four regions of the United Kingdom, working in a range of clinical settings with different levels of professional experience of DLD. The findings indicate that clinical assessment practices broadly align with the CATALISE statements. Although clinicians carry out standardised assessments more frequently than other types of assessment, they also gather information from other sources and use this alongside standardised test scores to inform clinical decisions. Clinical observation and language sample analysis are commonly utilised to evaluate functional impairment and impact, along with parent/carer/teacher and child report. However, asking about the child's own perspective could be more widely utilised. The findings also highlight a lack of familiarity with the details of the CATALISE documents among two thirds of the participants. Assessment practices broadly align with the CATALISE statements, but there is a need for greater clarity regarding terminology and the assessment of functional language impairment and impact. This research should prompt discussion in the profession about how to further develop and adopt expressive language assessment practices which reflect the CATALISE consensus and support effective assessment. What is already known on the subject The CATALISE consortium documents on Developmental Language Disorder (DLD) were published in 2016/17. The extent to which expressive language assessment practice in the United Kingdom reflects the new definition and statements on assessment has not previously been investigated. What this paper adds to existing knowledge This survey indicates that speech and language therapists in the United Kingdom assessing children for DLD mostly balance standardised language test scores with other sources of information in clinical decision-making, and utilise clinical observation and language sample analysis to consider functional impairment and the impact of the language disorder. However, important questions are raised regarding the robustness and objectivity with which these key parameters are currently defined and evaluated. What are the potential or actual clinical implications of this work? Clinicians, individually and at service level, are encouraged to reflect on their assessment of functional impairment and the impact of language disorder and to take steps to incorporate this where necessary. Professional guidance and clinical tools to facilitate robust, objective assessment would support clinical practice that aligns with expert consensus.