This paper examines the proposition that covariation information guides judgments about the dimensionality of attributions on the basis of causal principles of contrast and invariance, which are derived from Mill's methods of difference and agreement respectively. It is argued that the standard attribution categories specified in earlier research (e.g. person, occasion and stimulus) represent just one extreme of the attributional dimensions and require the principle of contrast, whereas additional attributional categories reflecting the opposite extreme of the dimensions (e.g. external, stable, general) require the principle of invariance. In three studies, subjects were given covariation information, and were asked to rate the properties of the likely cause along the dimensions of locus, stability, globality and control. In line with the predictions, consensus with others, consistency in time, distinctiveness between stimuli and contingency of one's actions showed the strongest effects on judgments of locus, stability, globality and control respectively. Similar results were obtained in a fourth study, where subjects had to judge the influence of eight causes with varying dimensional properties. Moreover, these judgments were rated somewhat higher given causes requiring the principle of invariance rather than the principle of contrast.