BACKGROUND Rhodiola rosea (R. rosea), a botanical of both western and traditional Chinese medicine, has been used as a folk remedy for improving stamina and reducing stress. However, few controlled clinical trials have examined the safety and efficacy of R. rosea for the treatment of major depressive disorder (MDD). This study seeks to evaluate the safety and efficacy of R. rosea in a 12-week, randomized, double-blind, placebo-controlled, parallel group study design. METHODS Subjects with MDD not receiving antidepressant therapy will be randomized to either R. rosea extract 340-1,360 mg daily; sertraline 50-200 mg daily, or placebo for 12 weeks. The primary outcome measure will be change over time in the mean 17-item Hamilton Depression Rating score. Secondary outcome measures will include safety and quality of life ratings. Statistical procedures will include mixed-effects models to assess efficacy for primary and secondary outcomes. CONCLUSIONS This study will provide valuable preliminary information on the safety and efficacy data of R. rosea versus conventional antidepressant therapy of MDD. It will also inform additional hypotheses and study design of future, fully powered, phase III clinical trials with R. rosea to determine its safety and efficacy in MDD.