Mentions of lettuce (Lactuca sp.) that have appeared since antiquity contained similar information on its curative properties, but such properties were ascribed to different species or varieties. Apart from the wild and poisonous lettuce, also garden or common lettuce were identified as having curative action, and some publications lacked information enabling the precise identification of the lettuce in question. In the 19th century, attempts were made to put some order into the knowledge of lettuce as a medicinal plant. Information on lettuce, contained in Polish medical studies of the 19th century, points to the poisonous species 'Lactuca virosa' and the common or garden lettuce 'Lactuca sativa v. Lactuca hortensis', as being used as a medicinal plant. In that period, lettuce and especially the desiccated lactescent juice obtained from it, ' lactucarium', were considered to be an intoxicant, and were used as a sedative and an analgesic. The action of the substance was weaker than that of opium but free of the side-effects, and medical practice showed that in some cases 'lactucarium' produced better curative effects than opium. To corroborate those properties of lettuce and its lactescent juice, studies were undertaken to find the substance responsible for the curative effects of the juice. However, such studies failed to produce the expected results, and the component responsible for the curative properties of letuce was not identified. Medical practice thus had to restrict itself to the uses of the desiccated lactescent juice and extracts obtained from it. The possibility of obtaining 'lactucarium' from plants cultivated in Poland caused Polish pharmacists and physicians to take an interest in the stuff and launch their own research of lettuce and the lactescent juice obtained from it. Results of research on lettuce were published in 19th-century journals by, among others, Jan Fryderyk Wolfgang, Florian Sawiczewski and Józef Orkisz.