The Canadian Registration Board of Occupational Hygienists (CRBOH) was established in 1986 to provide a registration system for professional occupational hygienists in Canada. It was decided that registration would be based on a competency examination following an appropriate combination of academic qualification and relevant professional experience. While the examination was being developed hygienists who met certain educational and experience requirements and who held other certifications by examination (such as those of the American Board of Industrial Hygiene, the British Examining and Board in Occupational Hygiene, or the Conseil d'Accrediation en Hygiene Industrielle du Quebec) were registered. In 1989 CRBOH, after much deliberation and review of other existing certification examinations, selected a two-part scheme consisting of both written and oral examinations. The written examination includes both multiple choice and essay style questions. Only those candidates successfully completing the written examination are eligible for the oral examination. The first group of candidates was examined in the fall of 1990. The authors outline the strengths and weaknesses of various forms of evaluation of professional competency. The rationale for the selection of the CRBOH examination format is discussed in relation to forms of evaluation currently being used in the United States and the United Kingdom. The implication of CRBOH registration on the training and education of occupational hygienists in Canada is highlighted.