The composition of the essential oils isolated from the needles of Pinus halepensis M., P. canariensis C., P. pinaster S., P. pinea L. and P. brutia grown in Morocco were investigated by CC and GC/MS. The oil of P. halepensis was found to be rich in monoterpenes hydrocarbons (78.1%), with alpha -pinene (23.3%) being the major component. The most abundant compound in P. pinea oil was also alpha -pinene (37.0%), while the oil of P. brutia contained beta -pinene (33.6%) as a major component. Sesquiterpene hydrocarbons were found to dominate the composition of P. canariensis (91.6%) and P. pinaster (64.6%), with the main components being germacrene D (62.5%) and beta -caryophyllene (22.2%), respectively. The oils and alpha -pinene, myrcene and beta -caryophyllene were tested for their inhibitory effect against 21 strains of bacteria. Examination of the antibacterial activity revealed that only P. pinaster and P. pinea oils exhibited a definite activity against all organisms tested. Compared to gentamicin, tetracycline and chloramphenicol, both oils showed a marked antiseptic activity.