Objective To observe the short-term effect of changing the sequence of PRP and MLP on the pre-proliferative or proliferative diabetic retinopathy patients with clinical significant macular edema (CSEM). Methods Sixty-three consecutive pre-proliferative or proliferative diabetic retinopathy outpatients (103 eyes) with clinical significant macular edema were selected and divided into two groups: 54 eyes in patients of group A accepted MLP one month prior to PRP and 49 eyes in patients of group B accepted the photocoagulative therapies in a contrary sequence. All the patients were followed up for 3 to 13 months and visual acuity. Light sensitivity of 5deg;macular threshold, and FFA were performed pre- and post-photocoagution. Results The improvement of visual acuity was found to be better in group A than that of group B (Plt;0.01) 2 months after the therapy, since then, there was no significant defference (Pgt;0.05) in both groups. Three and 4 months after the treatment, there was no significant difference in change of light sensitivity of 5deg;macular threshold in both groups. The macular leakages of 59 eyes, 32 ingroup A and 27 in group B, were well controlled. Conclusion Among the pre-proliferative or proliferative diabetic retinopathy patients with CSEM, visual acuity of those who accept MLP prior to PRP more rapidly than those who accept contrary sequence of photocoagulation, but the changing of therapeutic sequence might have no dramatic influence on light sensilivity of 5deg;macular threshold. (Chin J Ocul Fundus Dis,2000,16:150-152)