Two new diterpenes of the ent-trachylobane type were isolated from the stems of Xylopia langsdorffiana, ent-7alpha-acetoxytrachyloban-18-oic acid (1) and ent-7alpha-hydroxytrachyloban-18-oic acid (2). The structures of these isolates were deduced by spectroscopic data interpretation. X-ray crystallography of 1 was used to confirm its structure. The cytotoxic activity of 1 against V79 fibroblasts and rat hepatocytes was investigated.