Lactuca L. species belong to the Asteraceae family and these plants are traditionally used for therapeutic purposes around the world. The dried milky latex of L. serriola is known as "lettuce oil" and is used as a sedative in Turkey. This study aimed to evaluate the sedative effects and analyze the chemical compositions of latexes obtained from some Lactuca species growing in Turkey. The sedative effects were evaluated through various behavioral tests on mice. For this purpose, latexes were obtained from L. glareosa Boiss., L. viminea (L.) J. Presl and C. P, L. mulgedioides (Vis and Pani) Boiss. and Kotschy ex. Boiss., L. saligna L., and L. serriola L. The latex from L. saligna showed the highest sedative effects, whilst L. serriola and L. viminea latexes also displayed significant sedative effects compared to the control group at a dose of 100 mg/kg. However, the latexes from L. glareosa and L. mulqedioides did not exhibit any sedative effects on mice. Characteristic sesquiterpene lactones (lactucin, lactucopicrin, 11,13 beta-dihydrolactucin, and 11,13 beta-dihydrolactucopicrin) were determined qualitatively and quantitatively by high-performance liquid chromatography (HPLC). Lactucin was identified as the main component.