One of the psychological problems with highest prevalence is anxiety. The State Trait Anxiety Inventory is one of the instruments to measure it. This questionnaire assesses Trait Anxiety (understood as a personality factor that predisposes one to suffer from anxiety) and State Anxiety (refers to environment factors that protect from or generate anxiety). The questionnaire was adapted in Spain in 1982. Therefore, the goal of the study is to review the current psychometric properties of the STAI. A total of 1036 adults took part in the study. Cronbach's alpha reliability was .90 for Trait and .94 for State Anxiety. Factor analysis showed similar results compared with the original data. Moreover, differential item functioning (DIF) was carried out to explore sex bias. Only one of the 40 items showed DIF problems. Lastly, a t-Test was run, comparing the original and current values; whereas Trait Anxiety varied in 1 point, State Anxiety had differences of up to 6 points. In general, this result shows that the STAI has maintained adequate psychometric properties and has also been sensitive to increased environmental stimuli that produce stress.