in the tropical regions of South America such as Peru and Brazil. It is one of the oldest cultivated nonfood plants. More than 400 compounds have been isolated from different parts of cannabis plants and approximately 60 of them are cannabinoids or terpenic substances similar to Δ 9 -tetrahydrocannabinol (Δ 9 -THC) [1]. The only cannabinoids recognized by their psychoactive properties are Δ 9 -THC, Δ 8 -THC, and Δ 9 -tetrahydrocannabivarin (Δ 9 -THCV). Nevertheless, except for Δ 9 -THC, other active constituents are not present in signifi cant concentrations in the plants and probably do not contribute to the effects of Cannabis [2]. Nonactive cannabinoids tend to be present in signifi cant amounts, including cannabinol (CBN) and cannabidiol (CBD); the concentrations of every cannabinoid can vary depending on genetic factors, environmental conditions of the cultivation, the time of harvest, and other factors such as drying and storage conditions [3,4].On the basis of cannabinoid contents, cannabis plants are divided into "fi ber type" and "drug type." Applying a general formula for the percentage of the three main cannabinoids, it is possible to obtain the "phenotypic ratio," which can be used for the classifi cation of the plant [5]:Phenotypic ratio -THC %CBN %CBD = + %Δ 9 A phenotypic ratio greater than 1 indicates drug type. For forensic applications, there is a general consensus that a cannabis plant is defi ned as drug type when its leaves and infl orescences present a Δ 9 -THC content not lower than 0.5% [5].Gas chromatography (GC) and liquid chromatography (LC) coupled or not coupled with mass spectrometry Abstract A rapid and simple method was optimized for determination of Δ 9 -tetrahydrocannabinol (Δ 9 -THC), cannabidiol (CBD), and cannabinol (CBN) contents in cannabis products by gas chromatography with fl ameionization detection (GC-FID), using diazepam as internal standard. All parameters of validation of the method such as linearity, intraassay precision, and limits of detection and quantifi cation of the analytes were satisfactory. Using the described method, cannabinoid contents of 55 cannabis product samples seized in São Paulo City, Brazil, in 2006 and 2007 were measured. Δ 9 -THC content in marijuana and hashish samples varied between 0.08% and 5.5%, with an average of 2.5%. The phenotypic ratio showed that the products were able to be designated as "drug type."