Toxicological analysis of biological material encompasses searching for different toxic substances, amongst which drugs are a very important group. Confirmation of the presence of compounds in the amphetamine class is based on detection of particular compounds in this class, for example: amphetamine (AMF), methamphetamine (MAMF), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyethylamphetamine (MDEA), p-methoxyamphetamine (PMA) and p-methoxymethamphetamine (PMMA), using instrumental methods. In this paper we show the possibility of identification of contaminations originating from the synthesis of amphetamine using Leuckart’s method in biological materials from two autopsies performed in the Department of Forensic Medicine in Warsaw. In the first case we detected the presence of N-formylamphetamine, N,N-di-(β-phenylisopropyl) amine, N,N-di-(β-phenylisopropyl)methylamine, and derivatives of phenylmethylpyridine in stomach and blood samples. In the second case we found the same compounds only in the blood sample. Despite the lack of data about toxicity of these substances, it is possible that the toxicity may be comparable to that of amphetamine and its analogues.