Chemical investigation of the Australian ascidian Aplidium altarium led to the isolation of two new tyrosine derivatives, botryllamides K (1) and L (2), together with six known metabolites, botryllamides A–C (3–5), botryllamide G (6) and perspicamides A (7) and B (8). The structures of these compounds were elucidated by spectroscopic analysis. This is the first reported chemistry from this species. Compounds 1– 8 were evaluated for their cytotoxicity towards the tumour cell lines, MCF-7 (breast), H460 (lung) and SF268 (central nervous system).