This publication focuses on the production of docosahexaenoic acid (DHA; 22:6), an ω-3 polyunsaturated fatty acid with applications in foods and pharmaceuticals, by Crypthecodinium cohnii. This chloroplastless heterotrophic marine microalga has been studied since the end of the nineteenth century and has been identified as a good producer of DHA. C. cohnii can accumulate lipid to over 20% of its biomass dry weight, with a high content of DHA (over 30% of the total lipid). Other polyunsaturated fatty acids represent less than 1% of the C. cohnii-derived oil. The aim of the research described in this book was to identify relevant process parameters for the large-scale production of docosahexaenoic acid (DHA) with C. cohnii. Several cultivation protocols for C. cohnii were developed, analysed and optimised with respect to the production of biomass, lipid and DHA and solutions were sought for newly identified bottlenecks for industrial DHA production. g l-1, respectively.