The main Sartrean concepts and theses of freedom of will and unlimited responsibility, which seemed for many already outdated, are gaining actually interest in respect to the recent results in brain research. The main objective of the paper is to reevaluate Sartre's free will conception trying to answer the question: How would Sartre who, in the time of his existentialist phase during which his radical theory of freedom received its most pointed articulation, was familiar with psychological theories of determinism, have responded to statements of actually leading brain researchers such as "we are determined," "brain research liberates from illusions" or "I am my brain"?