Background: A continuation study of an extract of St. John's wort (Hypericum perforatum) for depression was performed in follow-up to an acute study that found no significant difference between St. John's wort extract and placebo. Method: Seventeen subjects with DSM-IV-defined major depressive disorder who responded to St. John's wort extract in the acute-phase study (phase 1) were continued on double-blind treatment with the same preparation for 24 weeks. Ninety-five subjects who did not respond to either St. John's wort or placebo were treated with an antidepressant for 24 weeks. Results: During antidepressant treatment, mean scores on the Hamilton Rating Scale for Depression for phase 1 nonresponders decreased significantly (p < .0001), with no significant difference between St. John's wort nonresponders and placebo nonresponders. Of the 17 subjects continued on treatment with St. John's wort extract, 5 (29.4%) relapsed. Conclusions: The subjects who did not respond to St. John's wort extract or placebo in phase 1 were, by and large, not resistant to antidepressant treatment. This suggests that the lack of efficacy found by Shelton et al. in the acutephase study was unlikely to be the result of a high proportion of treatment-resistant subjects. © Copyright 2004 Physicians Postgraduate Press, Inc.