In this article the urgency of a problem of safety of drugs application is stated, principal causes of complications of pharmacotherapy and the factors promoting occurrence of collateral reactions are analysed. Modern classification of collateral reactions is submitted. The special attention is given to the problems arising in practical activities at revealing of undesirable reaction. The methods of revealing and gathering of the information on collateral reactions developed by WHO, as well as the basic ways of their realization in Ukraine and in the European Community as a whole are described. In the conclusion there are submitted some results of the analysis of messages on collateral reactions to medicines and first steps of pharmacological vigilance in Ukraine.
