Four new guanacastane-type diterpenoids (1-4), together with the known compound, guanacastepene E (5), were isolated from a basidiomycete of the macro-fungi, Coprinus plicatilis 82. Their structures were elucidated on the basis of extensive spectroscopic analyses, including FT-ICR-MS, UV, IR and 1D and 2D NMR experiments. The in vitro cytotoxic activities of all compounds against the human cancer cell lines HepG2, HeLa, MDA-MB-231, BGC-823, HCT 116, and U2OS were evaluated, only compound 1 exhibited significant cytotoxicities with IC(50) values ranging from 1.2 to 6.0 μM.