Information scent is an establish concept for assessing how users interact with information retrieval systems. This paper proposes two ways of measuring user perceptions of information scent in order to assess the product quality of Web or Internet information retrieval systems. An empirical study is presented which validates these measures through an evaluation based on a live e-commerce application. This study shows a strong correlation between the measures of perceived scent and system usability. Finally the wider applicability of these methods is discussed.