The removal of several hormones and antibiotics by nanofiltration membranes was studied in mixed solutions. The effects of solution chemistry, organic matter and salinity were investigated on the rejection of tetracycline's and sulfanamides and selected hormones and their adsorption on membranes. Tetracyclines were observed to have a high adsorptive affinity for the membrane. Almost 80% of chlorotetracycline was adsorbed on the membrane surface compared with 50% for doxcycline while the adsorption rates for hormones were lower than those obtained for tetracyclines. Addition of calcium, organic matter and salinity had an influence on the rejections. Rejection of sulfanamides was low compared to hormones and tetracyclines. Addition of antibiotics to hormone solution increased the hormone rejections while almost complete rejections were observed for tetracyclines. (C) 2007 Elsevier B.V. All rights reserved.