The aim of this study was to investigate the effects of alendronate (Aln) irrigation with low-level laser therapy (LLLT) on the healing of bone defects in rats. Sixty Wistar rats weighing 250 to 300 g were randomly divided into three groups of 20 animals each: (1) control group, (2) Aln group, and (3) Aln with LLLT group. The distal epiphysis of all rats was perforated with a surgical bone drill. Twenty rats served as control. The bone defects of 40 rats received local alendronate sodium trihydrate irrigation (1 mg/ml) at the time of surgery. LLLT was applied to the bone defects of 20 rats immediately after Aln irrigation, and repeated on days 2, 4, 6, and 8 with a total dose of 10 J/cm(2) (2 J/cm(2) x 5). Continuous wave of GaAlAs laser (808 nm) was used with a power density of 0.1 W/cm(2). Laser energy was applied for 20 s (0.1 W x 20 s/1 cm(2)) per session. Control group, Aln group, and Aln with LLLT group rats were sacrificed at days 10 and 20 to compare the bone healing of each group histologically. There were significant differences between the three groups regarding union, substantia spongiosa, cortex formation, and in sum of histologic scores on days 10 and 20 (P < 0.0001). Our findings demonstrated that Aln has a more positive effect with LLLT on bone healing in rats. It was concluded that combining LLLT (808 nm laser at 10 J/cm(2)) with Aln irrigation has a beneficial effect in bone repair. It was demonstrated experimentally that Aln irrigation during the surgery had a significant effect to enhance bone formation, and LLLT significantly potentiated the osseous healing effects of Aln on bone defects. This administration method is able to minimize the dose of Aln in order to avoid both systemic and local adverse effects as well as the local injection times during the bone healing process.