Model. Emotion concepts are proposed to be organised according to a circular structure, a ``circumplex'', in a two-dimensional space of pleasure-displeasure and degree of arousal. Russell reviews the evidence from the literature before presenting his own experiments. The circumplex pattern was confirmed by several different methods for characterising emotion words: Russell used a categorisation and sorting method specifically designed for testing circularity, a grouping task providing similarity measures used for multidimensional scaling, and direct positioning on pleasure and arousal dimensions by means of semantic differential scales. All three methods yielded nearly identical circular patterns. From the domain of self-report of emotional state, similar distributions were obtained: Subjects reported their current emotional state on bipolar scales representing the emotion dimensions as well as on unipolar scales representing emotion adjectives. Regression analysis (prediction of the value on the adjective scale from the values on the emotion dimensions) as well as principal component analysis of the adjective ratings provided patterns very similar to the circular structure obtained in the concept characterisation tasks.