Volatile constituents and a hexane extract of the leaves of Halimium voldii Kit Tan, Perdetzoglou & Raus, sp. nova, were analyzed by GC and GC-MS. Thirty compounds were identified in the essential oil of Halimium representing 88.7% of the oil composition. The main components were nonanal (12.8%), dodecane (10.6%), Z-caryophyllene (8.2%), gamma-muurolene (10.9%), delta-cadidene (3.5%), caryophyllene oxide (5.1%), beta-eudesmol (3.6%) and manoyl oxide (5.5%). Thymol was identified in the hexane extract as the main compound. A labdane diterpene ent-labd-7, 13 (E)-dien, 15-ol was detected by its mass spectra fragmentation pattern and its structure was determined by spectroscopic methods and its optical rotation. The essential oil and the hexane extract were assayed for their antimicrobial activity against gram (+) and gram (-) bacteria.