Twenty seven com. foam-forming agents (FFA) were studied for chem. O demand. Some of the FFA were also studied for surface tension and biodegradability in aq. solns. of varying concn. The ratio of biolog. to chem. O demand after 5 or 20 days at 20 degrees C was used as a measure of the biodegradability. The protein and fluoroprotein FFA showed the lower biodegradability than the perfluorosynthetic ones in contrary to the former views (W.H. Ruppert et al., 2004). Literature data on the toxicity and environmental impact of FFA were also reviewed.