AbstractSeven female hypertensive subjects, being treated with an aqueous extract ofAdenia cissampeloides, (‘Adenia’), and seven weight‐, age‐ and sex‐matched hypertensive subjects about to begin treatment, were used to evaluate the therapeutic and possible toxic effects of this herbal preparation which is used at the Centre for Scientific Research into Plant Medicine (CSRPM), to control hypertension. Measurements of systolic and diastolic blood pressures were recorded, and serum levels of α‐hydroxybutyrate dehydrogenase (HBDH), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) were determined to give an indication of the effectiveness of ‘Adenia’ as an anti‐hypertensive agent. Serum levels of γ‐glutamyl transferase (GGT), alanine aminotransferase (ALT), alkaline phosphatase (ALP), bilirubin, proteins and cholesterol were used to indicate possible liver damage, and blood urea nitrogen (BUN), serum creatinine and creatinine clearance rate were determined for the assessment of possible nephrotoxicity. Systolic blood pressure was significantly lower in subjects on ‘Adenia’ compared to the control subjects not on ‘Adenia’. (p<0.01). HBDH and CK, were lower in the patients on ‘Adenia’, but the differences were not statistically significant. Levels of total and conjugated bilirubin were significantly lower in the subjects on ‘Adenia’, (P<0.05). The plant preparation appears not to ha