Previous work of the authors established the protein expression spectra of D-type cyclins, and found that there were differential expression in nasopharyngeal carcinoma (NPC) biopsies. Using Western Blotting, aberrant overexpression of the cyclinD1 protein in NPC cell lines is reported. CyclinD2 and cyclinD3, the other members of D-type cyclins, were also detected in NPC cell lines. A comparison of the expression patterns in the cell lines, positive or negative in the latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus, revealed that the expression of D-Type cyclin proteins might be increased by EBV-LMP1. The abundance of these proteins showed characteristic variation consistent with a cell- cycle-dependent oscillation and the peak levels expressed in G1 as analyzed by double-parameter flow cytometry. These data suggest that cyclinD1 is essential for cell cycle progression in G1 and may play a role in NPC carcinogenesis.