This article is from Metagenics Update Dec/Jan 2008 page14 

A simple herbal prescription may take the heat out of menopause. 77 peri- or postmenopausal women experiencing climacteric symptoms were treated with St. John's wort and Black Cohosh extract (standardized to 1 mg terpene glycosides and 0.25 mg hypericin respectively) or a placebo for 12 weeks. Treatment with the St. John's wort and Black Cohosh extract resulted in significant improvements in hot flushes at 4 and 12 weeks. In addition HDL -cholesterol decreased in the placebo group and increased in the treatment group, the difference between groups was statistically significant suggesting a beneficial effect on lipid metabolism.

Comment:

Hot flashes or flushes are the most common reason to seek treatment at menopause and are experienced by around 75% of women. This is the second clinical trial assessing the efficacy of the combination of St. John's wort and Black Cohosh, previously it was found that 16 weeks treatment not only reduced hot flushes but improved depressive symptoms as well, although depressive symptoms were not assessed in the current study. Considering the potential risks with two popular pharmacological treatments for menopausal symptoms, Hormone Replacement Therapy and Selective Serotonin Reuptake Inhibitors, the combination of St. John's wort and Black Cohosh may offer a safe and effective treatment option for many women.

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Chung DJ et al. Black Cohosh and St. John's wort for climacteric symptoms. Yonsei Med J. 2007 Apr 30;48(2):289-94