Adverse reactions induced by Chinese herbal injections have been frequently reported. However, the precise causes of these adverse reactions are not yet fully understood. The aim of the present study was to determine the role of chlorogenic acid (a ubiquitous component of Chinese herbs) in the toxicity of Chinese herbal injections. Beagle dogs were given chlorogenic acid, Yuxingcao injection, or Qingkailing injection (the latter two both containing chlorogenic acid) by intravenous (i.v.) injection, once a day for 7 or 9 days. The systemic toxicity was evaluated. An additional ultrastructural observation on liver and kidney was performed. Anaphylactoid reactions were obvious in dogs treated with Yuxingcao injection. Varying degrees of ultrastructural changes in liver and kidney were observed in the treated dogs, especially in dogs treated with Chinese herbal injections. Our study has led to the view that chlorogenic acid is not an allergen when administrated by i.v. injection, but liver and kidney injury induced by Chinese herbal injections can be partly attributed to chlorogenic acid.