This study investigated the effect of a weak magnetic field (50 microT, 20 Hz sinusoidal, 5 s duration) on concurrent perceptions of visual stimuli. Subjects were seated between Helmholtz coils and gave post-exposure ratings for the affective content and arousing nature of presented images. They were blind as to the presence or absence of a simultaneously presented field. Skin conductance and arousal ratings did not show significant differences between experimental and control conditions, but the affective content rating did (P = 0.041), with the images viewed under field exposure being rated as having a more positive affect. Such measures might thus be useful as additional indicators of magnetic field detection. A post-hoc analysis of skin conductance profiles showed that 48% of subjects exhibited a lowering of skin conductance during field exposure, 34% exhibited no apparent reaction, and 17% exhibited an increase. Overall ratings given by each of the groups appeared to relate to these physiological profiles.