Václav Jan Tomášek was one of the most important Bohemian musicians of the first half of the 19th century. He was a sought after composer, pianist and also a successful music teacher. As a composer, he laid down the foundations of modern Czech song writing to German and Czech texts, and in piano composing he helped the development of a new form – the ‘characteristic’ piece. The research carried out over the last five years shows that the sources relating to Tomášek’s life and work, are dispersed all over Central Europe. The most important collection, including the composer’s estate, survives in the National Museum – Czech Music Museum, Prague. The composer’s estate was presented to the Museum in 1874 by his heir and nephew, Baron Eduard Tomaschek. The full contents of the estate, which was not listed, are not exactly known. It seems that the collection contained most of Tomaschek’s compositions. There are more autographs and handwritten copies than printed scores. An unknown amount of non-musical documents, also inherited by the nephew Eduard, was, at the beginning of the 20th century, in the private collections of the music publisher M. Urbánek and F. Donebauer, from whom the Tomášek materials were acquired by R. Morawetz. Most of the documents, dealt with by the specialist press of the first three decades of the 20th century, are today considered lost. Discovery of V. J. Tomášek’s estate papers, including his last will, supported some traditional beliefs about the estate, and also brought completely new information.