OBJECTIVE To study the cell behavior of periodontal ligament cells (PDLCs) cultured on commercially pure titanium (cpTi) by cell morphology, cell counting and osteoclin (OC) immunofluorescent staining. METHODS 1 x 10(5)/ml PDLCs in 2 ml culture medium were seeded on cpTi discs fixed in 24-well culture plates. Morphological study of cell attachment was observed by scanning electron microscope (SEM) and fluorescence microscopy. Cell adhesion was analyzed by MTT at 0.5, 1, 2, 4 hours respectively. OC was directly observed by immunofluorescent staining. RESULTS PDLCs could attach and spread on cpTi discs. SEM showed that PDLCs had pseudopod-like protuberance. PDLCs showed different attaching phase and reached saturation in cell number at the early stage. The cells and ECM could express OC 7 days later. CONCLUSIONS PDLCs show a regular, dynamic pattern in early stage and they can keep proliferating and differentiating on CpTi in vitro. It was indicated that the biological function of PDLCs around dental implant should be reconsidered.