In　this　paper,　we　investigate　the　mixed　initial-boundary　value　problem　with　large　BV　data　for　linearly　degenerate　quasilinear　hyperbolic　systems　of　diagonal　form　with　general　nonlinear　boundary　conditions　in　the　half　space　{(t,x)　vertical　bar　t　＞=　0,　x　＞=　0}.　As　the　result　in　[A.　Bressan,　Contractive　metrics　for　nonlinear　hyperbolic　systems,　Indiana　Univ.　Math.　J.　37　(1988)　409-421]　suggests　that　one　may　achieve　global　smoothness　even　if　the　C-1　norm　of　the　initial　data　is　large,　we　prove　that,　if　the　C-1　norm　and　the　BV　norm　of　the　initial　and　boundary　data　are　bounded　but　possibly　large,　then　the　solution　remains　C-1　globally　in　time　and　possesses　uniformly　bounded　total　variation　in　x　for　all　t　＞=　0.　As　an　application,　we　apply　the　result　to　the　system　describing　the　motion　of　relativistic　closed　strings　in　the　Minkowski　space　R1+n.　(C)　2009　Elsevier　Inc.　All　rights　reserved.