Twenty-five new (abiesadines A-Y, 1-25) and 29 known (26-54) diterpenes were isolated from the aerial parts of Abies georgei. Abiesadine A (1) is a novel 8,14-seco-abietane, while abiesadine B (2) is a novel 9,10-seco-abietane. The structures of the new compounds were established on the basis of spectroscopic data analysis. Manool (52) showed the strongest effect against LPS-induced NO production in RAW264.7 macrophages with the IC(50) value of 11.0microg/mL. In another anti-inflammatory assay against TNFalpha-triggered NF-kappaB activity, (12R,13R)-8,12-epoxy-14-labden-13-ol (54) exhibited the strongest effect (IC(50)=8.7microg/mL). For antitumor assays, pomiferin A (26) and 8,11,13-abietatriene-7alpha,18-diol (29) both showed the most significant activity against LOVO cells (IC(50)=9.2microg/mL). While 7-oxocallitrisic acid (46) exhibited significant cytotoxicity against QGY-7703 tumor cells (IC(50)=10.2microg/mL).