Although there is a great heterogeneity of depressive states in bipolar patients, there is only one definition in international classifications for describing them. However, this variety seems particularly important to recognize because of the possible exacerbation of some of these bipolar depressive states by antidepressants. We aimed at assessing whether it is possible to distinguish different forms of bipolar depression using a dimensional approach. We characterized 60 bipolar patients with a Major Depressive Episode (DSM-IV) using a new tool (MAThyS; Multidimensional Assessment of Thymic States), assessing five fundamental dimensions (emotional reactivity, cognitive speed, psychomotor function, motivation, and sensory perception) of mood states. A cluster analysis using the items of the dimensional scale revealed two types of depressive state: group 1 (n = 38), which had a low score, is characterized by an inhibition in all dimensions, whereas group 2 (n = 22) is characterized by an overactivation. The emotional reactivity is the most relevant dimension for discriminating these two types of depression (group 1: hyporeactivity; group 2: hyperreactivity), whereas sadness is not. Bipolar depressive states are not homogeneous. A dimensional approach based on emotional reactivity could be useful for discriminating the different forms of bipolar depression. Bipolar depressions may be classified as hyporeactive or hyperreactive. This classification might have therapeutic implications, because hyperreactive depression should belong to the broad spectrum of mixed states.< Réduire