Phosphate activated glutaminase (PAG) was quantified in human cerebellar cortex extracts in 13 patients with Alzheimer's disease (AD) and 13 controls by Western immunoblotting using antibody to C-terminus of PAG kidney isoform. The majority of samples from the AD group contained less amount of PAG in comparison with control samples. Although medians in these groups were slightly different (21 and 28 arbitrary units in AD patients and controls, respectively), the Mann Whitney U-test demonstrated a significant between-group difference (U= 28.5, Z= -2.87, p=0.004). Since the both groups were matched for gender, age and postmortem interval, the difference in the PAG level was probably due to the presence of AD. The alteration in the PAG level observed in the cerebellum of patients with AD results in the disturbance of probably not only glutamate metabolism but also many other pathways involving PAG and leads to crucial consequences, particularly, to neurodegeneration.