Chlamydia pneumoniae is a common pathogen that causes upper and lower respiratory tract infections and is difficult to isolate from clinical specimens. Recently, we succeeded in isolating the first C. pneumoniae strain in Korea. This study characterizes the morphology, infectivity, and drug sensitivity of the Korean strain, designated LKK-1. Electron microscopy was performed for thin sections, and the infectivity over time was tested by counting the inclusion-forming units every 12 h. The minimum inhibitory concentrations of doxycycline, erythromycin, clarithromycin, ciprofloxacin, and levofloxacin were determined following the standard Japanese method. The elementary bodies of LKK-1 were round, like those in Japanese strain KKpn-1, whereas those of TW-183 have wavy cell membranes and are pear-shaped. The infectivity curve and drug sensitivities of LKK-1 were nearly the same as those of KKpn-1. In conclusion, LKK-1, the first strain from Korea, is similar to the Japanese strain KKpn-1 in terms of morphology, growth, and drug sensitivities, and shows a distinct difference in morphology compared with TW-183. Further studies are needed to elucidate the morphological differences between round strains and classical pear-shaped strains of C. pneumoniae.