Bioactive extracts from wild blueberries were isolated, fractionated, and analyzed. Antioxidant activity, cardioprotective capacity, and ability to inhibit the initiation stage of chemically-induced carcinogenesis were evaluated. Many fractions had antioxidant activity, especially those rich in anthocyanins and proanthocyanidins. The ease of isolation of bioactive compounds and the ability to obtain accurate bioassays depended strongly on the source material used. Extracts from spray-dried formulations containing magnesium citrate and tri-calcium phosphate provided easier materials for bioactivity assessment and demonstrated antioxidant, cancer preventive and cardioprotective activity. Extracts with potent antioxidant activity degraded readily, underscoring the need for rapid alternative fractionation tactics and rigorously controlled storage conditions.