The essential oils obtained from Crithmum maritimum L. (marine fennel) and two samples of Foeniculum vulgare Miller (common fennel) were analysed by GC and GC-MS and assayed for their antioxidant and antibacterial activities. The antioxidant activity of the oils was evaluated by two lipid model systems: a modified thiobarbituric acid reactive species (TBARS) assay and a spectrophotometric detection of hydroperoxydienes from linoleic acid in a micellar system. The oils demonstrated antioxidant capacities, comparable in some cases to that of alpha-tocopherol and butylated hydroxytoluene (BHT), used as reference antioxidants. Concerning the antimicrobial tests the essential oils were assayed against twenty-five genera of bacteria, including animal and plant pathogens, food poisoning and spoilage bacteria. Oils from the two samples of F. vulgare showed a higher and broader degree of inhibition than that of C. maritimum.