S100B, a calcium-binding protein produced by astroglial cells, mediates paracrine and autocrine effects on neurons and glial cells. It regulates the balance between proliferation and differentiation in neurons and glial cells by affecting protective and apoptotic mechanisms. Post-mortem studies have demonstrated a deficit in synapses and dendrites in brains of schizophrenics. Recent studies have shown increased S100B levels in medicated acutely psychotic schizophrenic patients as well as unmedicated or drug naive schizophrenics. One study reported a positive correlation between negative symptoms and S100B. S100B serum levels (quantitative immunoassay) and psychopathology (Positive and Negative Syndrome Scale, PANSS) were examined upon study admission and after 12 and 24 weeks of standardized treatment in 98 chronic schizophrenic patients with primarily negative symptoms. Compared to age- and sex-matched healthy controls, the schizophrenic patients showed significantly increased S100B concentrations upon admission and after 12 and 24 weeks of treatment. High PANSS negative scores were correlated with high S100B levels. Regression analysis comparing psychopathology subscales and S100B identified negative symptomatology as the predicting factor for S100B. S100B is not just elevated during acute stages of disease since it remains elevated for at least 6 months following an acute exacerbation. With regard to psychopathology, negative symptomatology appears to be the predicting factor for the absolute S100B concentration. This might indicate that S100B in schizophrenic patients either promotes apoptotic mechanisms by itself or is released from astrocytes as part of an attempt to repair a degenerative or destructive process.