In the cultivations of Cannabis, it is important to be able to distinguish fiber-type plants from drug-type plants by an easy observation of their phenotype. This study required the screening of manysamples for their cannabinoid content. A simple and highly sensitive time-resolved fluoroimmunological method was developed for the determination of Δ9-tetrahydrocannabinol in the leaf extracts.The useful range of the calibration curve was between 10 pg and 25 ng of standard. Matrix effectswere minimized by a high dilution of samples. Keywords: Δ9-Tetrahydrocannabinol; cannabinoids; Cannabis; TR fluoroimmunoassay; monoclonalantibody