Objective:To determine the season in which the Eastern Nigeria mistletoe,Loranthus micranthus,parasitic on Persea americana possesses optimum antidiabetic activity and to determine the seasonal variation in the constituents.Methods:The antidiabetic activities of the aqueous methanol extracts of the leaves of Eastern Nigeria mistletoe,Loranthus micranthus, harvested in two seasons of the year,the onset of rainy season(April) and the peak of rainy season(July) were compared.The tests were carried out on six(6) groups(A-F) of alloxaninduced diabetic rats.Groups A and B received 200 mg/kg and 400 mg/kg of the April sample extracts respectively while groups C and D received same doses of the July sample extracts. Group E and F which were the positive and negative controls received 10 mg/kg of glibenclamide and 2 ml/kg of 3%tween 20 respectively.The blood glucose levels of the animals were monitored hourly with a glucometer for six hours.The phytochemical analysis of the plant extracts were also carried out by standard procedures.Results:The results showed that group A and B exhibited significant(P<0.05) percentage reduction in the fasting blood sugar(FBS) level of the animals(38.9%and 39.2%respectively) with maximum reduction observed at the 5th and 6th hour respectively compared to glibenclamide(71.3%).Group C showed no significant (P>0.05) FBS reduction(15.9%) while group D exhibited highly significant(P<0.01) reduction (47.5%) with the maximum reduction occurring after 6 hours.The phytochemical analysis of the crude methanol extracts revealed the presence of carbohydrates,glycosides,saponins, tannins,flavonoids,steroids,terpenoids,acidic compounds,resins and oils.These were present in different proportions in both seasons.Conclusions:This study shows that there is a seasonal, dose-dependent variation in the chemical composition viz-a-viz the antidiabetic activity of the plant under study.This activity is highest at the peak of the rainy season. Objective: To determine the season in which the Eastern Nigeria mistletoe, Loranthus micranthus, parasitic on Persea americana possesses optimum antidiabetic activity and determine the seasonal variation in the constituents. Methods: The antidiabetic activities of the aqueous methanol extracts of the leaves of Eastern Nigeria mistletoe, Loranthus micranthus, harvested in two seasons of the year, the onset of rainy season (April) and the peak of rainy season (July) were compared. The tests were carried out on six (6) groups (AF) of alloxaninduced diabetic rats. Groups A and B received 200 mg / kg and 400 mg / kg of the April sample extracts respectively while groups C and D received same doses of the July sample extracts. Group E and F which were the positive and negative controls received 10 mg / kg of glibenclamide and 2 ml / kg of 3% tween 20 respectively.The blood glucose levels of the animals were monitored hourly with a glucometer for six hours. phytochemical analysis of the plant extracts were also carried out by standard procedures. Results: The results showed that group A and B exhibited significant (P <0.05) percentage reduction in the fasting blood sugar (FBS) level of the animals (38.9% and 39.2% respectively) with maximum reduction observed at the 5th and 6th respectively respectively compared to glibenclamide (71.3%). Group C showed no significant (P> 0.05) FBS reduction (15.9%) while group D extracted highly significant reduction occurring after 6 hours. The phytochemical analysis of the crude methanol extracts revealed carbohydrates, glycosides, saponins, tannins, flavonoids, steroids, terpenoids, acidic compounds, resins and oils. These were present in different proportions in both seasons. : This study shows that there is is a seasonal, dose-dependent variation in the chemical composition viz-a-viz the antidiabetic activity of the plant under study. This activity is highest at the peak of the rainy season.