This thesis addresses the issue of the subjective perception of the speaker's speed during simultaneous interpretation. The theoretical grounding of the thesis is based on Karla Déjean Le Féal's doctoral thesis (1978), which first introduced the notion of subjective speed, whereby two speeches of equal objective speed (as measured in syllables/min.) are perceived as having different speeds. The conclusions of Déjean Le Féal's thesis demonstrate that interpreters usually experience a faster subjective speed when interpreting speeches which were prewritten and then read aloud by the speaker. Impromptu speeches are usually perceived as being slower than read speeches. Aside from the above-mentioned theory of subjective speed, the theoretical section of this thesis analyzes various approaches to measuring speech speed, the relation between objective speed and simultaneous interpreting, the determinants of speech speed and prosodic features influencing the subjective perception of speed. The empirical section of this thesis consists of an experiment which aims to verify Déjean Le Féal's conclusions using French-Czech material. The methodology of the experiment partially replicates the method used by Aneta Mandysová in her master's thesis (2011), which is focused on German-Czech material. The method used...