Put-pose: To evaluate the short-term changes in pattern electroretinography (PERG) after photodynamic therapy (PDT). Methods: Thirty eyes of 30 patients (17 males, 13 females) with choroidal neovascularization secondary to age related macular degeneration were included in this study. Standard PDT with verteporfin was performed on each patient. Serial PERG recordings were performed before, 1 week, and 1 month after PDT. Results: Mean age of the patients was 69.6 +/- 8.4 years (range 56 and 90 years). One month after PDT, the visual acuity improved in 16 eyes, remained unchanged in 12 eyes and deteriorated in two eyes. New hemorrhages were seen in two eyes in the first week after PDT and visual acuity was decreased in those patients. No other patient complained of ocular and systemic adverse events. There was a statistically significant reduction in the amplitudes of P-50 and N-95 waves at the first week recordings after PDT. At 1 month after PDT, no significant differences in the P-50 and N-95 amplitudes were observed compared with pre-PDT PERG recordings. There were no significant changes in the latencies of P-50 and N-95 at the first week and first month recordings when compared with pre-treatment PERG values. Conclusions: Reduction in P-50 and N-95 amplitudes suggests that transient impairments in macular function occur at the first week after PDT.