In this chapter, the authors consider terpenoid molecules with oxygen-containing functional groups attached to the monoterpene and sesquiterpene skeletons. Molecules can have more than one functional group. As the functional group(s) of a molecule give it distinct properties, we can group molecules by their different functional groups. Terpenoid alcohols have a hydroxyl group attached to one of their carbon atoms. All monoterpenols have the monoterpenoid carbon chain of 10 carbon atoms and may contain a hydroxyl group anywhere along the chain. Primary alcohols are easily oxidised to aldehydes, secondary alcohols are oxidised to ketones, while tertiary alcohols are not oxidised at all. Monoterpenols are often less volatile than monoterpenes, and their boiling points correspondingly higher. Monoterpenols have been shown to have strong antibacterial and antifungal properties which, though not as strong as those of commercial disinfectants, have the advantage that they are usually mild on the skin and mucous membranes.