After his emigration from Hungary and a longer stay in Austria and Argentina, Dohnányi settled down in Tallahassee (USA) in 1949 and lived there until his death in 1960. Besides his professorship at the Florida State University (FSU) and his continuous concert-tours in the whole country, he was also very active as a composer in this decade. The ultimate composition of this period and his life is the Passacaglia for Solo Flute (op. 48. no. 2) which is a quite unusual piece of the composer, not only because of the choice of instrument, unprecedented in the œuvre, and its theme, partly dodecaphonic, but because of its significant source-material to be found in the Kilényi-Dohnányi Collection of the FSU. This paper attempts to study this last, odd piece of Dohnányi exhaustively through the investigation of its musical and non-musical sources in parallel with its analysis.