The cases of 127 consecutive patients with subarachnoid hemorrhage (SAH), in whom cerebral panangiography revealed no cause for the bleeding nor any sign of an intraparenchymatous hemorrhage, were reviewed in a study of the long-term prognosis and the possible prognostic factors in this condition. Data for all 127 patients in the study were obtained, with an average follow-up period of 5.4 years. After the 1st week post-SAH, only three rebleeds had occurred. In all, 80% of the patients had returned to full activity, 91% to at least part-time work; if the patients with hypertension were excluded, these figures rose to 86% and 95%, respectively. Decreased wakefulness on admission related to a slightly poorer prognosis, whereas age and red blood cell count in the cerebrospinal fluid had no prognostic significance. Of those patients who, at the end of the 2nd week following the SAH, were fully awake and had not developed any symptoms of delayed cerebral ischemia (87% of all patients admitted), 88% returned to full activity, 97% to at least part-time work. The survival rate for this group, as well as causes of death, seem to be within the range for normal individuals. It should thus be possible to inform these patients (at least the normotensive ones) of the benignity of their condition, directly after normal angiography. Even among the patients who were able to return to full activity, symptoms attributable to the SAH were common: 22% experienced problems such as frequent headaches, vertigo, irritability, and increased fatigability.