The monograph represents one of outputs from the solution of spruce monoculture conversions and their economic impact. The presented results were obtained from the analysis and synthesis of data concerning the effect of harmful agents onto forest stands in Natural Forest Region 16 – Bohemian-Moravian Upland. The analysis of harmful agents was related only to damages induced by logging and extraction, losses caused by underbark insects, honey fungus, snow and frost, and by a group of so-called obscure causes. The lowest average damage to the standing volume of spruce stands was observed in stand groups occurring in Forest Altitudinal Vegetation Zone 4. As to causes, the greatest damages to the standing volume of spruce stands were attributable to snow and frost. The rate of damage to the spruce standing volumes per 1 ha area in the respective age classes ranged from 0% to 66%. Risks of the occurrence of damage expressed by the percentage of spruce representation in the stands are illustrated by regression logarithmic functions, which indicate the relation between the occurrence of harmful agent and the spruce stand age. Based on calculations, coeffi cients were established for the percent risk of the occurrence of damage to standing volumes of stands in the respective Groups of Forest Types (GFT). Relevant coefficients of spruce utility value in individual edaphic groups of GFT were used to modify yield tables for spruce stands. Zdroj anotace: OKCZ - ANOTACE Z WEBU