This is an announcement for the paper "Tree metrics and their Lipschitz-free spaces" by Alexandre Godard. Abstract: We compute the Lipschitz-free spaces of subsets of the real line and characterize subsets of metric trees by the fact that their Lipschitz-free space is isometric to a subspace of $L_1$. Archive classification: math.FA math.MG Mathematics Subject Classification: Primary 46B04; Secondary 05C05, 46B25, 54E35 Remarks: 9 pages The source file(s), lip.bbl: 1919 bytes The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/0904.3178 or http://arXiv.org/abs/0904.3178 or by email in unzipped form by transmitting an empty message with subject line uget 0904.3178 or in gzipped form by using subject line get 0904.3178 to: math@arXiv.org.