the aim of this work was to analyze the composition of oriental cedar volatile oils (platycladus orientalis (l.) franco) obtained from leaves and cones, over one season cycle to study the effect of climate conditions on the chemical composition as well as antimicrobial activities of the collected oils. the oils yield varied according to the plant part as well as the season of collection. the major chemical components of the samples among the seasonal cycle were -pinene, -cedrol and 3-carene. spring leaves and cones oils were the most active against e. coli, autumn leaves oils were the most active against s. aureus, while autumn cones and leaves oils were the most active against c. albicans. opls-da indicated that p-cymen-7-ol and -muurolene were positively correlated to activity against s. aureus, -funebrene and tricyclene were correlated to activity against e. coli while o-cymol and -phellandrene were the positive contributors against c. albicans.