The object of this study was to investigate the assumption that a detailed explanation and description of gastroscopy to a patient reduces his fears of the procedure. In order to check this assumption, 243 consecutive patients who underwent elective gastroscopy were randomly distributed to 4 groups: Group A received a standard brief description of upper G-I endoscopy by the treating physician; Group B patients were given a detailed description by the endoscopist himself; Group C was given a comprehensive explanation and was shown an album of pictures illustrating each stage of the procedure; Group D saw a specially prepared video film of the procedure. A fifth group, E, consisted of patients who had previously undergone upper gastrointestinal endoscopy. Patient anxiety was measured using the "Spielberger State and Trait Anxiety Scales". According to the scoring on these scales there was no significant difference between the groups, thus showing that increasingly detailed description of the procedure did not diminish patients' fear. Neither did ethnic background or age have any significant influence on these results. Higher education had marginal influence on patients' apprehension about the procedure. However, female patients had significantly higher anxiety state and trait anxiety scoring than men. If endoscopy can be taken as typically representative of all invasive procedures, these results may have a much more general application.