The production of ketocarotenoids (KCs) from Chlorococcum sp. strain MA-1 was investigated by a two-step process. In the first step, 18 g biomass l(-1) was achieved by feeding glucose to the heterotrophic cultures; in the second step, the high-density cultures were treated with light illumination or chemical stress in dark, respectively, to induce KC synthesis. Light-treated cultures could produce 103 mg total KCs l(-1) and 32 mg astaxanthin l(-1), three times higher than those from chemical-treated cultures, in the 10 days of induction. The percentages of individual KCs (hydroxyechinenone, canthaxanthin, adonirubin and astaxanthin) in the total KCs were not markedly influenced by the different stress conditions. The developed two-step process provides a feasible strategy for commercial production of ketocarotenoids by the green microalga, Chlorococcum sp. strain MA-1.