ISA Certification is a voluntary program that tests and certifies a professional’s achievement of a standard level of knowledge and skill in the field of arboriculture. When a professional becomes an ISA Certified Arborist, they should be recognized by their peers and the public as a tree care professional who has attained a generally-accepted level of knowledge in areas such as tree biology, diagnosis, maintenance practices, safety, and other subject and practice areas within the tree care profession as identified through periodic job task analyses.