The aim of this study was to elucidate the brain processes preceding penile responses. Electroencephalographic (EEG) potentials and penile circumference were recorded simultaneously while male subjects were exposed to visual sexual stimuli (VSS). The trials were sorted by the penile response of the subjects (erection, maintenance or detumescence). The corresponding EEG recordings were then subjected to independent component analysis. We found that 200 ms after VSS onset brain potentials differ according to the genital response to follow. Whereas early posterior negativity (EPN) was predominantly related to erection and maintenance, P3-like activity was found to precede detumescence. EPN indicates a more 'emotional' processing state of the brain, whereas P3-like activity related to detumescence indicates a more 'cognitive' processing state. The latter is assumed to reflect activity of the locus coeruleus-norepinephrine system. Further research should evaluate the contribution of P3-related brain activity to psychogenic erectile dysfunction.