AbstractSynthesis of a range of 1‐, 2‐and 3‐phenyl, benzyl and phenethyl substituted cyclopentanols and cyclopentylmethyl alcohols and related unsaturated compounds is reported. Results of bioassays of their esters with known pyrethroidal acids against two species of insect lead to recognition of some structure‐activity relationships in this series. The distance and relative orientation between the alcoholic and aryl functions appears crucial, but in other respects the nature of the spacer group between them is less important. The most effective alcoholic components are based on cyclop