Background Methyl aminolaevulinate photodynamic therapy ( MAL- PDT) is an effective treatment for Bowen disease ( BD) of the lower extremities. Er: YAG (erbium:yttrium-aluminium-garnet) ablative fractional laser ( AFL) treatment removes the stratum corneum to increase MAL uptake and may improve efficacy. However, no studies have directly compared the efficacy of MAL- PDT with and without Er: YAG AFL therapy in treating BD of the lower extremities in Asians. Objectives To compare the efficacy, recurrence rate, cosmetic outcomes and safety between Er: YAG AFL-assisted MAL- PDT (Er: YAG AFL- PDT) and standard MAL- PDT. Methods Twenty-one patients with a total of 58 BD lesions randomly received either one session of Er: YAG AFL- PDT or two sessions of MAL- PDT in two symmetrical areas. Er: YAG AFL therapy was performed with 550-600 μm ablation depth, level 1 coagulation, 22% treatment density and a single pulse. MAL cream was then applied under occlusion for 3 h and illuminated with a red light-emitting diode lamp at 37 J cm−2. A second session of MAL- PDT was administered 7 days later. Overall response rate, recurrence rate, cosmetic outcomes and safety were assessed at 1 week, 3 and 12 months after treatment. Results After 3 months, Er: YAG AFL- PDT was significantly more effective (93·8%) than MAL- PDT (73·1%; P = 0·031), and the recurrence rate was significantly lower for Er: YAG AFL- PDT (6·7%) than MAL- PDT (31·6%) at 12 months ( P = 0·022). No significant difference was found between Er: YAG AFL- PDT and MAL- PDT in terms of cosmetic outcomes or safety. Conclusions Er: YAG AFL- PDT showed significantly higher efficacy and lower recurrence rate than did standard MAL- PDT for treating lower extremity BD in an Asian population. [ABSTRACT FROM AUTHOR]