The feasibility of the long-term (> 170 days) culture of a dinoflagellate microalga in a raceway photobioreactor is demonstrated for the first time. Amphidinium carterae was chosen for this study as it is producer of interesting high-value compounds. Repeated semicontinuous culture provided to be a robust operational mode. Different concentration levels of the f/2 medium nutrients (i.e. f/2 x 1-3) were assayed. The composition f/2 x 3 (N:P = 5), combined with a sinusoidal irradiance pattern (L/D = 24:0) with a 570 mu E m(-2) s(-1) daily mean irradiance, maximized the biomass productivity (2.5 g m(-2) day(-1)) and production rate of the valuable carotenoid peridinin (19.4 +/- 1.35 mg m(-2) L-1 with nearly 1% of the biomass d.w.). Several carotenoids and polyunsaturated fatty acids were also present in significant percentages in the harvested biomass (EPA, 1.69 +/- 0.31% d.w.; DHA, 3.47 +/- 0.24% d.w.), which had an average P-molar formulate of C40.7O21.2H73.9N3.9S0.3P1.