Interest in folklore was apparent in Jonas Basanavičius still at school, and the first folksongs he recorded from his mother. He collected folklore also when studying at the gymnasium and at the university in 1866–1874.
Along with songs, J. Basanavičius recorded folktales, proverbs, riddles, folk medicine, etc. He started publishing the collected folklore materials since the end of the 19th century.
In 1892 J. Basanavičius addressed the Lithuanian intelligentsia in periodicals like Varpas and Žemaičių ir Lietuvos Apžvalga encouraging them to collect folklore and send it to him. His first big work on folklore was ‘The Lithuanian Tales. I. Materials for the Lithuanian Mythology’, published in America in 1898. In 1902, the second volume of the ‘Lithuanian Tales’ appeared. It should be noted, that these two volumes comprised the first big collection of Lithuanian folktales published in Lithuanian.
In 1899–1900 J. Basanavičius published an address in the Lithuanian American press and that in the Lithuania Minor, asking readers to collect folktales. The materials submitted by the folklore recorders were subsequently published in big collections; thus, four volumes of ‘Various Lithuanian Tales’ appeared (vol.1 in 1903, vols.2, 3 in 1904, vol. 4 in 1905).
In 1902, the ‘Folksongs from Ožkabaliai’ were published in America. The book comprises over 400 of songs.
In 1903, another book of folk narratives was publihed, namely, ‘From the Life of Souls and Devils’. It comprises 823 place legends, folk belief legends and folk belief texts, reflecting the Lithuanian beliefs in mythical beings: e.g., devils, souls, ghosts, the deceased, incubi, spirits, etc. The same publication comprises an exhaustive study ‘Regarding the Souls and the Cult of the Dead among the Ancient Lithuanians’ by J. Basanavičius himself.
When the Lithuanian Science Society was founded in 1907, initiating the large-scale collection of folklore was among its prime tasks. In 1910, a short brochure was published, entitled ‘A Short Program for Collecting Folklore Items’. The repeated addresses and encouragements produced a response: a significant collection of folklore manuscripts was accumulated at the Lithuanian Science Society in a rather short time.
In 1926, the series ‘Lithuanian People’ published the last big publication of folklore edited by J. Basanavičius, namely, ‘The Lithuanian Laments’.
As J. Basanavičius became increasingly involved in various social activities, he lacked time to work with folklore manuscripts, and therefore quite a significant part of them remained unpublished. For instance, a bulky collection of folktales and legends, which had formerly belonged to the collections of the Lithuanian Science Society, was for a long time subsequently preserved at the Lithuanian Folklore Archives. This collection had been compiled by J. Basanavičius’ brother Vincas. It was published only in independent Lithuania, as vol. 8 of the Jonas Basanavičius Folklore Library, entitled ‘Tales and Legends from Ožkabaliai’. The vol. 11 from this series, ‘Miscellaneous Folklore from Collections’ comprises materials from the periodicals Mitteilungen der Litauischen litterarischen Gesellschaft and Aušra, while folk jokes about Strazdas and some other pieces of folklore saw publication for the first time here. Likewise, the vol. 12, ‘The Black Book’, was also published for the first time from manuscripts. It comprises a bulky file, containing data purposely collected by different recorders regarding popular beliefs, magic, superstitions and folk medicine. Some legends, folk prayers and curses can also be found here. The biggest share of such material was recorded by a devoted folklore collector, craftsman Matas Slančiauskas, who sent as many as 1100 texts to J. Basanavičius.
Along with folklore collection and publication, J. Basanavičius was an active and innovative researcher of Lithuanian culture. He wrote articles on history, he published a number of studies and reviews on various issues of Lithuanian folklore (he was particularly interested in folksongs and the mythical images reflected in them, as well as in ancient Lithuanian religion and mythology).
Having become increasingly interested in the comparative research on Thracs and Balts, J. Basanavičius was especially active in promoting an original theory of the origins of the Baltic peoples. In 1907, he published a study on ‘Lion in Lithuanian Tales and Songs’. This work is among his attempts to search for arguments supporting his theory on the Lithuanian ethnogenesis; in this case he analyzed the motif of lion, using folklore texts and pictures from ancient art. The subsequent study ‘Details from Thracian and Lithuanian Mythology’ was also written to support the same theory. Although J. Basanavičius spared neither time nor effort while attempting to ground his theory of Lithuanian ethnogenesis, he did not manage to persuade the scientific community in plausibility of his ideas, thus his theory remained no more than a hypothesis.