Samples of Xylaria humosa, a rare species of Xylariaceae, were collected during an investigation into the diversity of the fungus in the Phu Khieo Wildlife Sanctuary, Thailand. Nine compounds were isolated from the species and their structures elucidated by spectroscopic methods. The compounds were ergosterol (1), ergosterol peroxide (2), two meroterpenoids, chevalone B and C (3-4), together with five indole alkaloids, tryptoquivaline L (5), tryptoquivaline M (6), fiscalin A (7), epi-fiscalin A (8) and epi-fiscalin C (9). Compounds 2-9 exhibited variable cytotoxic activity against KB, NCI-H187 and MCF-7 cell lines.