The authors recently reported that over the years, the outcome of aneurysm surgery improved, and that surgical complications importantly affected this change. The present study was conducted to determine whether the incidence of symptomatic vasospasm in fact changed during the period under review, and the factors contributing to any changes. Between 1990 and 1995, 219 Hunt-Hess grade I to III patients with ruptured intracranial aneurysm underwent surgery within 3 days of subarachnoid hemorrhage ; all operations were performed by the same surgeon. Age, Hunt-Hess grade on admission, Fisher grade, hypertension, and hydrocephalus were analyzed to determine which factors were significant for syptomatic vasospasm, and for the periods 1990 to 1993, and 1994 to 1995, the distribution of each significant factor was then examined. Syptomatic vasospasm decreased significantly (p<0.05), but was seen in 28 of 124 patients(22.6%) treated beween 1990 and 1993 and 11 of 95(11.6%) treated between 1994 and 1995 ; no significant reduction of syptomatic vasospasm as a cause of mortality and morbidity (irreversible vasospasm) was seen, however, Fisher grade(p<0.05) and Hunt-Hess grade(p<0.05) significantly contributed to the development of symptomatic vasospasm, though the distribution of these two biologically significant factors was not statistically different. The question of whether or not surgery aggravates symptomatic vasospasm is controversial, and symptomatic vasospasm is, in addition, still an ill-defined disease entity. Except for the occurrence of fewer surgical complication and the fact that the incidence of reversible symptomatic vasospasm was less during the second period of treatment, no differences were found in the distribution of factors which significantly influenced symptomatic vasospasm, and this suggests that surgery affects the development of reversible symptomatic vasospasm. On the basis of increased risk of cerebral ischemia associated with surgery in vulnerable ischemic brain resulting from subarachnoid hemorrhage, the use of the term 'delayed ischemic neurologic deficit' after such hemorrhage appears to be more suitable than 'symptomatic vasospasm'.