A new tetralin glucoside [1], named aceratioside, has been found to be a weakly cytostatic (PS ED50 9 micrograms/ml) constituent in leaves produced by the Australian rain forest tree Aceratium megalospermum. Structural determination of aceratioside was primarily accomplished with results from a series of acetylation, methylation, and high field nmr (including heteronuclear multiple bond correlation) experiments.