The determination of toxic substances in insect larvae collected from corpses in an advanced state of putrefaction can help to elucidate the causa mortis in forensic cases. In this study, an analytical method for the simultaneous determination of six prescription drugs, cocaine and its metabolite benzoylecgonine, and aldicarb and its sulfone and sulfoxide metabolites in larvae was developed and validated. The method involved a solidliquid extraction with low temperature partitioning, and determination by a liquid chromatography-mass spectrometry (LC-MS-MS) method. Significant matrix effects were observed for most analytes, indicating the need to use analytical curves in pre-extracted fortified matrices. The limits of quantification ranged from 1 to 40 ng/g, with precision between 2.83 and 16.9 %. The validated method was used to analyze 28 actual larval samples collected from corpses at the Forensic Medical Institute between 2009 and 2012 in the Federal District, Brazil. At least one substance was present in 11 samples. Benzoylecgonine and diazepam were found in four samples each, followed by cocaine (three samples), carbamazepine (two samples) and amitriptyline (one sample). The method proved to be simple, fast and of low cost, and can be used by forensic laboratories as a complementary tool to elucidate intoxicationrelated deaths where usual toxicological matrices are not available.