Tree of heaven is one of the most widespread alien tree species in Slovenia. Because of relatively low data on its distribution it was eleborated the distribution map of Ailanthus altissima in Goriška. It is evident from the map that tree of heaven is the most common along water courses, roads, lines, in the vicinity of the villages and on abandoned agricultural land. On 4 selected plots was analyzed the way of reproducing of Ailanthus altissima. The findings have shown that spreads aggressively both by seeds and vegetatively by root sprouts. Within 3 sample plots was observed the ecological situation in the stands. The results showed that the possibility of spreading is lower when the rate of surface stoniness and rockiness is higher. Where it has been present for decades, it successfully spreads and replaces indigenous tree species.