We identified 15 patients with serological evidence of current Chlamydia pneumoniae infection when we studied 263 patients with central nervous system infections among an adult population of 3 million in 1993. In 9 of the 15 patients no other associated or etiological agents were found. One patient died. Sequelae appeared in 7 patients. In neurological infections, C. pneumoniae may be more prevalent as an associated agent than appreciated, and adequate antibiotic therapy may be life-saving.