Previously, we reported that a 1-butanol soluble extract of the edible red alga Palmaria palmata, known as dulse, exhibited hydroxyl and stable free radical scavenging activity as well as inhibition of lipid peroxidation, attributed to the reducing activity and polyphenol content of the dulse extract. In the present study, we evaluated the antioxidant and antiproliferative activities of two grades of dulse harvested from Canadian Maritime locations differing in UV radiation exposure (i.e. west versus east coasts of Grand Manan Island, New Brunswick). The 1-butanol soluble extract from Grade 1 dulse (reduced UV-exposure) exhibited lower reducing activity versus Grade 2 dulse (greater UV exposure) reflecting a lower requirement for endogenous antioxidant protection. Grade 1 and 2 dulse extracts both inhibited (p0.03) AAPH-induced lipid peroxidation, but had no effect on AMVN-induced lipid peroxidation, demonstrating the aqueous nature of the antioxidants involved. The Grade 1 and 2 dulse extract inhibition (p<0.05) of HeLa cell proliferation was dose-dependent over 0.5-5.0mg/mL and maximal at 48 and 72h incubation. The antiproliferative effects of the Grade 1 and 2 dulse extracts in the present study likely reflect the bioactivity of the polyphenol content of these extracts.