The State - Trait Anxiety Inventory (STAI) is composed of two scales which intend to measures state (STAI-S) and trait (STAI-T) anxiety components. State anxiety refers to a transitory emotional state characterized by subjective feelings of tension that may vary in intensity over time whereas trait anxiety represents a relatively stable disposition to respond to stress with anxiety and a tendency to perceive a wider range of situations as threatening. Several studies indicate that STAI-T latent structure presents two factors. Different interpretations have been raised to explain the nature of these factors. One of them proposed that that one factor is composed by items which express the presence of anxiety, such as tension and worry whereas the other factor seems to be related with items which express the absence of anxiety, such as rest, stability and satisfaction. However, other studies pointed out that one of these factors might be related to humor, more specifically depression. Therefore, the present study further investigates the factor structure of the STAI-T in three different Brazilian samples with distinct characteristics: a) students from two different Universities from Rio de Janeiro; b) high school students from Brasilia and c) marine subjects during a military draft. Results indicated that STAI-T factor structure depended on the sample investigated. University and high school students presented a factorial structure convergent with the anxiety and depression interpretation. On the other hand, the military sample presented a factorial structure based on the anxiety present anxiety absence interpretation. Theoretical aspects related to the ability of instruments to discriminate anxiety and depression are discussed.