OBJECTIVE: To investigate the effectiveness of low-level laser therapy (LLLT) as an adjunct to a program of eccentric exercises for the treatment of Achilles' tendinopathy.DESIGN: Randomized controlled trial with evaluations at baseline and 4, 12, and 52 weeks.SETTING: Primary care clinic.PARTICIPANTS: Participants with midportion Achilles' tendinopathy were randomly assigned to 2 groups (LLLT n=20: mean age ± SD, 45.6±9.1y; placebo n=20: mean age ± SD, 46.5±6.4y). The 12-week evaluation was completed by 36 participants (90%), and 33 participants (82.5%) completed the 52-week evaluation.INTERVENTION: Both groups of participants performed eccentric exercises over a 3-month period. In addition, they received either an active or placebo application of LLLT 3 times per week for the first 4 weeks; the dose was 3J per point.MAIN OUTCOME MEASURES: The primary outcome was the Victorian Institute of Sport Assessment-Achilles' questionnaire (VISA-A) score at 12 weeks; secondary outcome was a visual analog scale for pain. Outcomes were measured at baseline and 4, 12, and 52 weeks.RESULTS: Baseline characteristics exhibited no differences between groups. At the primary outcome point, there was no statistically significant difference in VISA-A scores between groups (P>.05). The difference in VISA-A scores at the 4-week point significantly favored the placebo group (F(1)=6.411, sum of squares 783.839; P=.016); all other outcome scores showed no significant difference between the groups at any time point. Observers were blinded to groupings.CONCLUSIONS: The clinical effectiveness of adding LLLT to eccentric exercises for the treatment of Achilles' tendinopathy has not been demonstrated using the parameters in this study.