The chemical investigation of the essential oils from the aerial organs of Bellis perennis L., the common daisy, showed that polyacetylenes were one of the dominant class of compounds. The major constituents, methyl deca-4,6-diynoate and deca-4,6-diynoic acid, and their structural analogues, deca-4,6-diyne, dimethyl octa-3,5-diyne-1,8-dioate and deca-4,6-diyne-1,10-dioic acid, were synthesised and their antimicrobial activity evaluated. Only deca-4,6-diynoic acid and deca-4,6-diyne-1,10-dioic acid showed antimicrobial activity, being the two compounds mainly effective against Gram-positive and Gram-negative bacteria, respectively. Structure-activity relationships of the tested polyacetylenes are discussed.