Platelet derived growth factor (PDGF) was identified as a powerful mitogenic growth factor which is released from activated platelets and has a marked activity as vasoconstrictor agent. In the present study we have measured cisternal cerebrospinal fluid (CSF) levels of PDGF in 72 patients operated on for intracranial aneurysm in order to verify whether it might be related to the clinical aspects of SAH with special regard to symptomatic vasospasm. CSF samples were obtained at surgery by cisternal puncture of the subarachnoid cistern the nearest to the aneurysm before aneurysm isolation and exclusion. The specimen were frozen in liquid nitrogen and stored at -80 degrees C until analysis. PDGF was measured using a commercially available reagent. Values are expressed as pg/ml of CSF. In 18 cases no radiological and clinical signs of SAH were detected and the mean cisternal CSF level of PDGF was 885.0 +/- 104.5 pg/ml; 20 patients were operated on between day 1 and 3 from the last SAH episode: mean cisternal CSF level of PDGF was 1917.5 +/- 459.4 pg/ml. In 34 patients treated with delayed surgery protocol, mean cisternal CSF level of PDGF was 995.3 +/- 73.8 pg/ml. Statistical analysis showed significant differences between groups (P: 0.011). In the subgroup of patients operated on within day 3 after SAH, 6 presented vasospasm and had mean cisternal CSF PDGF level which was significantly higher (P < 0.01) than in 14 patients without vasospasm. In the delayed "surgical" patients there was no significant difference in cisternal CSF levels of PDGF considering the occurrence of vasospasm. The results of the present study suggest that (a) after SAH there is a significant release of PDGF early after SAH and (b) higher levels of PDGF found in cisternal CSF of patients operated on within 72 hours after SAH may be predictive of symptomatic vasospasm.