Methadone is the main therapeutic option in heroin addiction treatment, but also an abuse substance. Given the analytical focus on the diagnosis of drug abuse and the usefulness of toxicological analysis methods in both overdose and monitoring substitution therapy, this study was aimed at the semi-quantitative determination of methadone by using Thin Layer Chromatography (TLC). By having the advantage of simplicity and rapidity, TLC finds its rightful place among the analysis methods when other relatively costly methods that involve instrumental performance are not available. METHODS TLC plates (silicagel GF 254 Merck), developing system methanol: strong ammonia 100: 1,5, photometric quantification at 254 nm, using TLC Scanner 3 (Camag). RESULTS The results show that methadone can be determined semi-quantitatively in the chromatographic conditions mentioned in the two domains tested (5 - 40 microg and 10 - 80 microg), with the best results obtained in the 5 - 40 microg domain. CONCLUSIONS Semi-quantitative TLC evaluation proposed by us has as main advantages the rapidity, simplicity and relatively low cost compared to other useful methods.