The nutrient removal and growth capacity of the cyanobacterium Phormidium bohneri were studied on daily anaerobic effluent. Among the three concentrations of effluent used (30, 40 and 50 mg N-NH3 litre(-1)), the highest growth rate (0.58 d(-1)) and final biomass (565 mg dry mass litre(-1) after 16 days) were found in the more dilute effluent. The removal rare of ammonium nitrogen during the first 6 days was similar for all treatments and was equal to 3.1 mg N-NH3 litre(-1) d(-1). In contrast, the rate of removal of phosphorus was proportional to the amount of phosphate present in the medium, with a maximum value of 4.9 mg P-PO43- litre(-1) d(-1). The cellular concentrations of chlorophyll a and phycobiliproteins were followed as a function of rime. In all treatments a decrease in chlorophyll a content, from 1.8 to 0.7% of the dry mass, was observed. In contrast, after an initial decrease from 9.6 to 4.0% of the dry mass, the content of phycobiliproteins increased during the next 6-8 days of growth to reach about 6.0% of the dry mass after 10 days. It is concluded that the growth of P. bohneri on dairy anaerobic efficient is feasible for the production of a useful biomass in parallel to tertiary treatment.