This book presents a systematic and analyzed available - own and published data of heavy metals pollution of Bulgarian soils and developed relationships between the amount of heavy metals in the fraction of (i) SOM, (ii) available forms and (iii) total content of heavy metals in Bulgarian soils. It is investigated the variability of pollution in different regions and their comparative characteristics by statistical methods of analysis and established relationships between some parameters associated with the processes of humus formation and equations are derived describing the relationships established (i), (ii),( iii).