Photodynamic therapy (PDT) is a promising treatment for nasopharyngeal carcinoma. However, recurrence and metastasis of the tumor after PDT remains problematic. In this study we investigated VEGF and PCNA expression in tumor tissues after 5-ALA-PDT. BALB/c nude mice with NPC tumors of similar size were randomly assigned to three groups (n=10 each). In the two treatment groups, mice were administrated 5-ALA intratumorally at a dose of 100 mg/kg and 3-3.5 h prior to laser irradiation (630 nm, 100 J/cm(2), 100 mW/cm(2)). The mice in one of the treatment groups were sacrificed at 24 h after PDT. The other treatment group and control group mice were sacrificed 14 days after PDT, and the tumor weights were determined for all three groups. Mean tumor weights at 14 days after PDT were 1.353+/-0.204 g in the treatment group and 3.124+/-0.380 g in the control group (p<0.001). Results showed the VEGF level in tumor tissues at 24 h after PDT was slightly higher than that in the control group, while it was down-regulated at 14 days after PDT. The PCNA level was not significantly different in tumor tissues among the three groups, but it was lower in degenerated tumor cells 24 h after PDT. Our results suggest that VEGF may play a role in tumor recurrence and metastasis following PDT. Residual tumor cells escaped from PDT is the main reason for tumor recurrence.