The authors investigated the biodegradability and toxicity of polyoxyethylene-alkyl citric diester-triethanolamine(PAT), which is one of new non-ionic detergents. 1) The PAT is very biodegradable, which 50% is biodegraded for one day and 100% for eight days by the activated sludge treatment and 40% for one day and 93% for eight days by the aerobic domestic sewage treatment. 2) $LD_{50}$ of PAT for chicken, mouse, and rat by oral adminstration are 7.1g/kg, 8.4g/kg and 14.0g/kg reactively. 3) $TL_{m}$ of PAT for goldfish is 64.0mg/l in 24bours. 4) No reaction for humun skin is determined by PAT.