During the 2001, 2002, and 2003 enterovirus seasons, we investigated the correlations between cerebrospinal fluid (CSF) nucleated cell counts and elevated CSF protein levels and the detection of enteroviral RNA by reverse transcription (RT)-PCR. Our objective was to determine if pleocytosis and/or elevated protein levels were predictive of positive RT-PCR results for enterovirus. We were also interested in determining if the presence of West Nile virus during the 2002 enteroviral season contributed to a change in these correlations. We found that in the group of patients aged < 2 months, the absence of pleocytosis was highly predictive of a negative RT-PCR result. Elevated CSF protein level was not a good predictor of RT-PCR positivity for enterovirus and did not add to the diagnostic sensitivity or specificity of pleocytosis.