Odor detection thresholds of n–hexanol, n–hex–trans–2–en–ol, n–hex–2,4–dein–1–ol, n–hept–trans–2–2–en–l–ol, n–oct–trans–2–en–1–ol and the corresponding aldehydes in water were determined using a constant stimuli, single sample presentation method. All compounds were carefully purified before use and the concentration of alcohols and aldehydes in the stock and sniff solutions was routinely checked along with the sniffing work. The odor threshold values of both the C-6 alcohols and C-6 aldehydes were found to increase with unsaturation in the order saturated C-7> >C-8 for the 2-monounsaturated compounds. All the alcohols tested had significantly higher odor thresholds values than the corresponding aldehydes, the mean ratio varying from 20.8 to 259 for the five pairs. The importance of these findings in relation to food flavour is discussed.