The benzoyltropeine was difficult to differentiate from tropacocaine, of which it is an isomer, because of the lack of analytical data on it. The laboratory techniques used included thin-layer chromatography (TLC), gas chromatography (GC), high-resolution gas chromatography (HRGC), nuclear magnetic resonance (NMR), and gas chromatography/mass spectrometry (GC/MS). Results showed TLC and HRGC to be the most suitable for differentiation between the two substances. A specific identification of isomers of these substances was obtained by using nuclear magnetic resonance and GCMS techniques. This differentiation is important because benzoyltropeine has often been found in recent seizures of heroin in Italy. This heroin was mainly destined for international illicit drug trafficking and particularly for the market in North America. Figures, table, and 4 references. (Author abstract modified)