Stephen P Myers,1 Ann M Mulder,1 Don G Baker,1 Shelley R Robinson,1 Margaret I Rolfe,2 Lyndon Brooks,1 J Helen Fitton,3 1NatMed-Research Unit, Southern Cross University, 2University Centre for Rural Health, Sydney School of Public Health, The University of Sydney, Lismore, NSW, 3Marinova Pty Ltd, Cambridge, TAS, Australia Purpose: Preliminary investigation of a fucoidan with demonstrated reduction in the symptoms of osteoarthritis (OA) of the hip and knee. Patients and methods: A double-blind randomized controlled trial was carried out to determine the safety and efficacy of a 300 mg dose of a Fucus vesiculosus extract (85% fucoidan) over a 12-week period in a population (n=122) with mild-to-moderate OA of the hip and knee as measured by the validated instrument "Comprehensive Osteoarthritis Test." Safety was measured by assessing cholesterol, liver function, renal function, and hematopoietic function, and closely monitoring adverse events. Result: Ninety-six participants completed the study. The reduction in symptoms of OA was not significantly different from the placebo response. There were no changes in the blood measurements that were of any clinical significance during the course of the study. Conclusion: The F. vesiculosus fucoidan extract was safe and well tolerated. At a dose of 300 mg, the extract showed no difference in reduction of OA symptoms from the placebo. Keywords: joint pain, clinical trial, seaweed, polysaccharide