Prospective remembering was studied in a group of patients who suffered from Herpes Simplex Encephalitis (HSE). All patients showed a marked deficit in executing intentions for future actions under all the given constraints. The deficit extended to both time- and event-based intentions. The analysis of errors showed somewhat different patterns and some dissociations with evidence for selective preservation or damage to specific components involved in prospective remembering. These patients, in fact, may fail because of a difficulty in taking into account all given constraints or in activating stored intentions and in forming intentions or in remembering the content of the actions. Time- and event-based tasks seem to show different sources of errors also in the same patient.