Ambroperuvin is a new pseudoguaianolide isolated from Ambrosia peruviana Willd., a plant used in traditional medicine in Venezuela. The analysis of the X-ray powder pattern being reported led to an orthorhombic unit cell with space group P 2 1 2 1 2 1 and cell parameters a = 15.999(6) Å, b = 11.263(2) Å, c = 9.112(2) Å. No detectable impurities were observed.