Sildenafil is widely used to treat male erectile dysfunction. Two cases of men who developed Generalized TonicClonic Seizures (GTCS) after taking sildenafil have been reported previously, suggesting its proconvulsant effect . Of 33,724 people who had side effects while taking sildenafil, eight (0.02%) experienced myoclonus . Further information except for the age (≥60 years), the duration of taking, and concomitant conditions and drugs is not available. We describe the case of a man who developed myoclonus after taking sildenafil and discuss a probable mechanism for generation of myoclonus.