Poisonous plants have deteriorated the livestock sector in the past and are still among the current problems of the Trakya Region where livestock is densly located. It is reported that, in herbal poisoning not only the species of the plant but also the identification and characterisation of included active substances is very important in diagnose and treatment. For this, it was tried to practically determine the spread of poisonous plants in Trakya Region and qualitative determination of the active substances they include. A study was conducted in this region, mainly around the places with dense livestock for two years and a map showing the spread of poisonous plants was prepared. It has been observed by field trials that, extremely poisonous plants such as Arum italicum. Datura stramonium. Echalliitme laterium, Euphorbia spp., Hypericum perforatum, Papaver rhoeas. Sinapis arvensis. Sorghum halepense, Tribulus terrestris were widespread in region. Isolation and identification of active agents included in Arum italicum, Coichicum autumnale, Conium macula-turn. Datura stramonium. Digitalis ferruginea, D. lanata, D. viridiflara., Equisetum spp., Hypericum perforatum. Hyoscyamus albus, Melilotus officinalis, Nerium oleander, Quercus spp., Papaver rhoeas. Solanum nigrumre Solanum dulcamara which were gathered from different places of Trakya Region were done by colour reaction and Thin Layer Chramatography (TLC) techniques and most pratical methods were determined for diagnosis of herbal poisonoings.