Arboriculture (from the Latin arbor = tree, cultura = tending or caring) is tree cultivation based on tree biology. The term arboriculture is often loosely used and includes the care of other woody plants such as vines (in the United States), wall shrubs (in England), and climbing shrubs (in Australia). This relatively young discipline generally focuses on single trees or small groups of trees, usually in urban areas. Arboriculture is an essential and integral part of urban forestry and is sometimes treated as a special type of horticulture. The goals of arboriculture are to establish and maintain healthy, aesthetic, and safe trees. These goals are met through the selection of suitable tree species for harsh urban conditions, proper planting, watering, fertilization, mulching, protection (stakes, supports), and formative pruning of new plantings as well as through proper training, regular pruning, vitality and safety inspections of mature trees. This chapter deals with the assessment of trees and the most commonly applied tree care practices: pruning, crown stabilization and wound treatment. Targeted tree care should rely on knowledge of their growth and response to adverse urban conditions inducing the decrease of tree vitality and simultaneous increase of hazard problems. Among several methods for assessment of tree vitality, visual methods will deserve most attention due to their practical value. Identification of dangerous trees and decision for solution of the problem is a highly responsible procedure, which demands expertise in tree biology and diagnostic methods. Hence, the process of walling-off of infected and decayed wood tissue and a range of methods used for assessment of hazard trees will be considered in this chapter.