Using marine Chlamydomonas as food, the food requirement of bisexual brine shrimp Artemia franciscana was estimated in terms of nitrogen in order to assist production. The ingested food was theoretically fractionated to the maintenance, somatic growth and reproduction of nauplius and cyst. While feeding marine chlamydomonad (5 pg N/cell) to the shrimp (Lmm), the daily maintenance ration was almost proportional to the cube of body length (2.952) and was 2844 cells/shrimp/day for shrimp of 1mm length at 28°C. On the basis of ingested food, the somatic food conversion efficiency was 67%. The efficiency of nauplius production was 23% and that of cyst production was 44%, based on the food taken by a pair of shrimps. Including the reproductive products as growth, the gross conversion efficiency was 16% in the groups from which the maintenance ration and somatic conversion factor were obtained, and 24% in the groups from which the reproductive conversion factors were obtained. The reproductive growth per total growth increased with the body length and the feeding rate, and was zero below 5.7mm in length and 1.0 times the daily maintenance ration.