The vast majority of microorganisms cannot be cultured under laboratory conditions. It was estimated that over 99% of microbial genetic information are inaccessible due to the inability to isolate and culture bacteria. It is also widely known that among those uncultured organisms there are such that bear the genes which are interesting from the biotechnological point of view, i.e. coding for novel enzymes (lipases, amylases, cellulases, polymerases etc.), responsible for resistance to various chemical substances (heavy metals, aromatic compounds, pesticides, antibiotics), or the genes encoding the elements of biosynthetic pathways (for instance producing novel antibiotics). Recently, the methods have been developed that allow (i) isolation and purification of environmental DNA, (ii) construction of random fragment libraries of such DNA, and (iii) effective screening of those libraries in search for interesting genes. These methods are collectively known as ?metagenomics' or ?environmental genomics'. We aim to review the metagenomic methods, which will be done in Part I of our paper, and to present the up ? to ? date achievements and future perspectives for obtaining biotechnologically important genes from environmental samples in Part II. The main attention will be paid to soil metagenomics, as this kind of environment seems to be the most promising in terms of microbial biodiversity and the spectrum of biochemical reactions performed by inhabiting bacteria. We will treat the perspectives for isolation of novel, useful genes such as those coding for biosynthesis of antibiotics, organic compounds degrading pathways, and heavy metal resistance and prospects for their biotechnological application. Assessing the microbial biodiversity through metagenomic methods will also be covered.