The inappropriate use or the abuse of potentially toxic or psychoactive plants obliges the toxicologist analyst to adapt and improve his analytical techniques. Several papers about LC-MS/MS for the determination of the most current poisons such as atropine and scopolamine (deadly nightshade, datura), oleandrine (pink bay-tree), taxol (yew), cevadine and veratrine (hellebore), colchicine (meadow saffron), atractyloside (glue thistle) and digitaline (foxglove), were already published. We present here some examples of the use of LC- MS/MS triple quadrupole with reversed pliase chromatography for the detection of less common poisons such as glycyrrhetic acid (liquorice), LSA (morning glory seeds) and muscarine, muscimol and ibotenic acid (fly agaric mushrooms). After enzymatic hydrolysis, the total acid glycyrrhetic was quantified in biological samples by LC-MS/MS. Acquisition was carried out on four daughter ions (m/z = 189, m/z = 235, m/z = 149, m/z = 119) of the parent ion of glycyrrhetic acid (m/z = 471). The detection limit was about 0.5 ng/mL. This method was applied to two real cases. Case n°l: in an occasional consumer having ingested 5 rollers of liquorice candy over 8 hours, glycyrrhetic acid concentrations were of 13.7 ng/mL in blood and 75 ng/mL in the urine, 15 hours after the last ingestion. Case n°2: in a case of death invol¬ ving a chronic intoxication, glycyrrhetic acid concentrations were: cardiac blood: 7.6 ng/mL, vitreous: 5.1 ng/mL, urine: 18.2 ng/mL, gastric content: 83.3 ng/mL. The development of the detection of LSA in LC-MS/MS was carried out by direct infusion of methanolic maceration of Ipomea violacea seeds. Three daughter ions were acquired: m/z = 223.3, m/z = 207.5 and m/z = 180.3, fragments of the protonated molecular ion (m/z - 268.3). The analysis carried out on seized seeds showed a concentration of LSA of 99 ng/seed, expressed in LSD-d3 equivalent. A calibration in urine, carried out by additions of the maceration, solution, lead to estimated detection and quantification limits at 0.5 ng/mL and 1 ng/mL, respectively. The detection by LC-MS/MS of the active agents of fly agaric mushrooms was carried out by fragmentation of the molecular or pseudo-molecular ions of muscarine (m/z = 174.2), muscimol (m/z = 115.1) and ibotenic acid (m/z = 159.0). This method enabled us to determine concentrations in dry mushrooms of muscimol: 3.6 and 97.2 mg/kg, acid ibotenic: 16.4 and 216.8 mg/kg, and muscarine: 39.7 and 2006.0 mg/kg, in the feet and the heads, respectively.