The diagnostic significance of phosphoglycerate mutase (PGM) B-type isozyme activity capable of being inducible under hypoxia at the gene level as a serum marker for cerebral stroke was investigated. The normal level (mean +/- 2 SD) in human serum was determined to be 38 +/-18 units/L. Within 2 h after the onset of cerebral stroke (n = 65), B-type isozyme activity was elevated to 68 +/- 36 units/L, and retained to be higher level until 1-3 days. Serum B-type isozyme activities of 52 survival cases and 13 dead cases, being judged at the period of 1-2 months after the onset, were retrospectively compared; B-type isozyme activity that had been measured within 24 h after the onset was significantly higher (81 +/- 42 units/L) for the dead cases than for survival cases (57 +/- 27 units/L) with P < 0.05. These results suggest that serum PGM B-type isozyme has the potential as a novel marker for diagnosis of cerebral stroke and its severity.