Clozapine is undoubtedly the most effective treatment of resistant schizophrenia. New international guidelines for clozapine use were published recently. The aim of this paper is to familiarize Polish readers with the guideline containing the most recent data on this subject. The information included in the clozapine package insert is based on old studies and needs actualization. Newer studies bring information about the prevalence of certain serious adverse events connected to clozapine treatment. They also suggest that ethnicity can be a significant factor in clozapine metabolism. One of the ways to prevent adverse events caused by clozapine is by measuring C-reactive protein (CRP) and troponin concentrations. The authors also point out the need for clozapine concentration measurements as a guide to estimating the final dose. We hope that this paper will help popularize the safe use of this extraordinary drug based on the most recent data.