The leaves of Ocimum gratissimum (OG) and Vernonia amygdalina (VA) had been of medicinal interest mainly due to their respective antioxidant and antihyperglycaemic properties. A daily dose of 0.5gKg-1 body weight aqueous leaf extracts of OG, VA and 50:50 (OG+VA) was orally administered to three different rabbit groups for 28 days, fed ad libitum. The control group was given only 2mlKg-1 of normal saline daily. Fasting blood glucose concentration was monitored with a digital glucometer. From the SPSS (version 15) multivariate analysis (p=.05), results showed that the mean fasting blood glucose concentrations of normal rabbits used was 5.98±0.5 mMolL-1. Only VA lowered fasting blood glucose within 24 hours and maintained the hypoglycaemia for 72 hours; VA potentiated OG after 72 hours and later synergistically lowered fasting blood glucose concentration. This study suggested that VA and (OG+VA) were time-dependent hypoglycaemic: while consumption of VA had acute effect, (OG+VA) could preferably be used for longer prophylaxis of diabetes. Therefore, further researches are recommended on the efficacy of this herbal combination therapy.