A new tetracyclic biscembrane hydrocarbon, trocheliane (1), along with two new cembranoid diterpenes, sarcotrocheldiol A (2) and B (3), and the known diterpene cembrene-C (4), were isolated from the Red Sea soft coral Sarcophyton trocheliophorum. The structures and relative stereochemistry of the compounds were elucidated by interpretation of MS, 1 D NMR, and 2 D NMR experiments. The sensitivity of some pathogenic bacteria used as test organisms to the new compounds 1-3 was determined. 1 showed appreciable antimicrobial activity with the diameter of inhibition zones ranging from 11 to 18 mm. 1 was active against the two multidrug resistant bacteria Acinetobacter baumannii and Staphylococcus aureus. Minimal inhibitory concentrations (MICs) of compound 1 were recorded for all the tested bacteria using the fluorescein diacetate method and the recorded MIC values ranged from 4 to 6 $\mu $M.