Abstract： Objective To investigate the clinical efficacy of photodynamic therapy using low concentration of photosensitizer, short incubation time and red light source in the treatment of ache. Methods Thirty patients with facial ache were equally randomized into two groups, one group applying 5% 5-aminolevulinic acid (ALA) to the facial lesions on the right side and placebo agent on the left side as control, the other applying the same concentration of ALA to the facial lesions on the left side and placebo agent on the right side as control. The whole face of every subject was irradiated with red light once a week for 4 sessions. The lesions were counted by a dermatologist, sebum production was measured by a sebum meter (SHP88) and pigmentation index by Mexameter MX 18, at the baseline and on week 2, 4, 8 after the last treatment. Adverse effects were also recorded at each visit. Results Two weeks after the last treatment, a sixty percent or more clinical improvement was achieved in the ALA-treated side of 25.9% patients, but no patients experienced sixty or more percent clinical improvement in control side, and the efficacy of ALA was superior to that of the placebo (P<0.05). A significant reduction was noticed in the count of every kind of lesions, including comedo, papules, pustules, cysts/nodules, as well as the total count of these lesions compared with the baseline (all P<0.05); meanwhile, only the pustule count and total count of lesions were decreased in the control side (both P<0.05). Conclusions Both ALA (5%)-PDT and red light-irradiation alone can reduce the number of acne lesions, but the former is more effective than the latter with few side reactions.