INTRODUCTION: Hallucinations are frequent in clinical practice, with an incidence of up to 38.7% in the general population. We aim to determine the prevalence of hallucinations among healthy young adults in our environment. SUBJECTS AND METHODS: We designed an observational study, using as subjects, 3rd to 6th year medical students of the Universidad Complutense de Madrid who complete clinical rotations in the Hospital Clínico San Carlos. After a screening questionnaire, an individual interview was conducted via telephone or e-mail to those students who reported hallucinations. We obtained clinical and epidemiological data through a semi-structured clinical interview performed by a third year Neurology resident. RESULTS: N=134 (average age was 22.1 years; 77.6% were women). 74 respondents answered affirmatively to one or more screening questions, and 54 completed the follow-up interview. 22.2% described visual phenomena and 64.8%, auditory. The majority reported sleep-related experiences and auditory perceptions related to hyper vigilance, such as hearing the telephone or the doorbell ring when in fact it had not (38.8%). All subjects had good insight and none had psychotic symptoms. Two cases were associated with substance abuse. CONCLUSIONS: Hallucinations are frequent among the general population. Traditionally, auditory phenomena have been associated with psychotic pathology, and other studies show a low population incidence (0.6%). However, in our sample, short auditory perceptions with immediate insight were frequent and not pathological.