Internationally, the assessment of nursing clinical performance has remained a challenge at undergraduate and postgraduate level. The clinical performance assessment tool (CPAT) was developed to measure paediatric intensive care (PIC) and adult critical care (ACC) postgraduate nursing students' developing clinical performance. The CPAT was based upon the Australian Competency Standards for Specialist Critical Care Nurses1, which are recognised as the professional standards for specialist level critical care nurses in Australia. A two phase descriptive correlational study was undertaken to examine the applicability, validity and reliability of the CPAT. Data collection included experienced clinical nurses' validation of the CPAT (Phase 1), the students' and assessors' documentation using the CPAT and individual semi-structured interviews (Phase 2). The revised CPAT, incorporating the second edition of the competency standards2, was further evaluated (Phase 3) by reviewing how the document had been used and surveying students and assessors. The findings supported the format and approach based on the ACCCN competency standards. The CPAT facilitated assessors to assist students to develop their clinical performance. However, substantial refinement and modification of the CPAT was required to make it useful as a clinical assessment tool. The significance of this was supported by the subsequent research examining the construct validity of the competency standards. However, the link with the ACCCN competencies remains evident, and this indirectly further supports the utility of having nationally agreed standards for professional practice within specialty areas.