The present work investigated biofilm development and process parameters in the nitrification of a synthetic saline wastewater (50 g l(-1) NaCl) in reactors known as ＇submerged aerated biological filters: The support used for biofilm development was made of PVC wrinkled plates with large specific area (138 m(2) m(-3)) and high porosity (> 95%). Biofilm development on the support was investigated by cultivating the mixed culture batchwise. In the first week of operation: a brown biofilm was macroscopically evident on the support surface. After 10 days the biofilm activity became stable, an ammonia removal rate of 2 g NH3 m(-3) h(-1) was observed and the attached biomass reached a maximum value of 172 mu g cm(-2) When the system was operated continuously, with a hydraulic retention time of 15 h, the removal efficiency observed was 94% in the absence of NaCl and 48% in the presence of 50 g l(-1) NaCl.