This programme of research is concerned with a direct comparison between the ways in which we respond to, and become aware of, subliminal and psi stimuli. I define subliminal percepts as those produced by sensory stimulation below the awareness threshold; psi "percepts", i.e. telepathy, clairvoyance and precognition, are those occurring in the absence of any physical stimulus. Initially a preliminary investigation was run to choose suitable target stimuli and to ascertain the correct subliminal volume. Then an exploratory study was run in which 10 participants undertook six Ganzfeld sessions each. The Ganzfeld technique induces the hypnagogic state and is a successful and well-researched design in parapsychology. Besides measuring levels of awareness to the stimuli, affective, physiological and personality factors were assessed. In the follow-up study, the basic design and targets were refined, and more extensive psychological tests were included; a semantic differential test, a state of consciousness report, and cognitive flexibility tests. The final study was run in order to assess whether the basic findings would generalise to a wider segment of the population. Results from the exploratory and follow-up studies indicate that, at the cognitive level of response, the psychological process of achieving awareness of the target is very similar for both phenomena. The final study indicated that awareness of subliminal stimuli is possibly relatively greater under certain circumstances. All three studies indicated that both phenomena are affected by factors such as attitude and personality in a similar manner.