The availability of phosphorus to juvenile abalone, Haliotis discus hannai from primary, secondary and tertiary calcium phosphate, primary sodium or potassium phosphate separately or in combination was determined in a 120-day feeding trial. Seven semi-purified diets were formulated to contain relativelyconstant dietary phosphorus, ranging from 0.78%-0.82%. The concentrations of dietary phosphorus were presumed to be slightly below the requirement for abalone.A brown alga, Laminaria japonica, was used as a control diet. Abalone juvenilesof similar size (average weight 1.18 g; average shell length 18.74 mm) were distributed in a single-pass, flow-through system using a completely randomized design with eight treatments and three replicates each treatment. The survival ranged from 71.1% to 81.1%, and was not significantly (P>0.05) related to dietary treatment. However, the weight gain rate (41.72%-65.02%), daily increment in shelllength (36.87-55.07 μm) and muscle RNA-DNA ratio (3.44-4.69) were significantly (P