Restriction endonuclease enzyme (XbaI) is a cutting enzyme and as such was used to characterize the organism. Of the 124 samples collected from different locations in Mid-Western Nigeria, 95(76.61%) were positive while 29(23.38%) were negative for Chlamydia pneumoniae by DNA isolation. The enzyme cut the DNA of Chlamydia pneumoniae at several points as visualized on agarose gel placed on ultra-violet illuminator. Only 3 DNA could not be cut by this enzyme. This shows strain variation.