The goal of this masters thesis was to make an arboricultural assessment of natural value trees in the Novo mesto IRSNC regional unit, with the purpose of finding out if the natural value trees in their current condition pose any kind of safety threat to surrounding infrastucutre and human lives. In total 41 natural values or 48 individual trees were examined in 11 municipalities in may 2018. The most common assessed tree species was the largeleaved lime (Tilia platyphyllos Scop.) (67 %), followed by cornish oak (Quercus petraea (Matt.) Liebl.) (7 %), european oak (Quercus robur L.) (4 %), European cornbeam (Carpinus betulus L.) (4 %), European pear (Pyrus communis L.) (4 %) and others. The average tree height measured was 21,3 m, the average circumference 469 cm and the average breast height diameter 149,3 cm. The results show that the trees are in bad condition. 52 % of the trees have a limited growing site. 18 % of trees had its trunk covered in moss and 11 % of trees had either growths or mechanical wounds on the trunk or their trunk was vertically ribbed. Only one tree had zero wounds or special features on the trunk. 29 % of the analyzed trees had mechanical wounds in the tree crown, 28 % had dead branches in the tree crown and 17 % had an asymmetrical tree crown. Of all the analyzed trees we detected atleast one mechanical wound, in at least one part of the tree. The results show that because of their bad condition, the trees pose a significant threat to surrounding infrastrucure. 5 trees were observed to be in critical condition and require immediate attention. Each Individual tree was also given a recommended arboricultural course of action if needed, based on the European tree pruning guide. With proper arboricultural procedures, the health condition of the trees could be greatly improved, which would in turn also greatly reduce the threat that they pose to surrounding infrastrucure and also human lives.