Although experimental research has confirmed the capacity of the human cognitive system to process information that does not reach consciousness (unconscious perception), empirical evidence of the incidence of subliminal verbal messages included on audiotapes claiming to improve human resources and correct some behavioral problems is meager and inconsistent. Our study assesses the influence of “subliminal tapes” designed to increase self-esteem. Participants were randomly assigned to four experimental conditions. One group listened to a tape of music with supra- and subliminal messages; another listened to a tape of music with only subliminal messages; the third group's tape had only music, although the participants believed that it also included subliminal messages; a fourth (“waiting”) group heard no tapes, but filled in the same self-esteem scales. Participants in the first three groups filled in the Tennessee Self-Concept Scale (Fitts, 1965) before and after listening to the tape for several days. All groups showed a similar pretest-posttest improvement in self-esteem (p ≤ .003), except for the waiting group, which did not improve (p = .311). This implies that only a placebo effect took place. Our data are not in accordance with those obtained by other authors. We comment upon the possible reasons for these discrepancies.