The streams from domestic wastewater treatment plants have been considered as a valuable medium for mass cultivation of algal biomass. The aim of this paper is to evaluate and compare the performance of Chlorella vulgaris and Scenedesmus dimorphus when domestic wastewater effluent after sand filter-UV disinfection and Bold Basal's Growth Synthetic Medium (BBM) are used as media. The trials were carried out in an effective volume of 0.4 L erlenmeyer flasks, operated at constant aeration with filtered air at a temperature of 26 +/- 2 degrees C, photoperiod of 16:8 light:dark cycles, and 35-40 mu mol photon m(2).s(-1) light density. Runs were started approximately with an optical density of 0.4 at 10 and 40 mg NO3-N/L concentration for BBM and wastewater effluent. Algal biomass was assessed daily by means of optical density (680 nm), chlorophyll-a and dry weight. Nitrate nitrogen, nitrite nitrogen, phosphate and pH were also analyzed. The maximum cell growth rate of Chlorella vulgaris was found to be nearly 2-folds of Scenedesmus dimorphus. Chlorophyll-a measurement had a parallel trend with optical density. Effective nitrogen removals were achieved at the end of the sets.