In this short report the evidence is given (based on the analyses of 22 case samples) that noscapine can be used as an adulterant in illicit heroin samples. In this context, the appearance of illicit heroin samples characterised by a high noscapine content (up to 61%) and a high noscapine/whole morphine ratio (up to 3.5) is highlighted. All samples discussed in the paper (132) were seized in Slovenia, in the period from 1997 to 1999 and were analysed by gas chromatography-mass spectrometry.