The monitoring data collected from 2000 to 2011 at the National Monitoring Station in Nha Trang bay showed that the seawater in this bay is clean, according to the national standard criteria of Vietnam (2008), although concentrations of the measuring parameters have been changedover time. However, two parameters (hydrocarbon, HC and total coliform) regularly exceed the standard values of the Vietnamese national criteria (QCVN: 2008/BTNMT) and ASEAN for bathing, recreation and aquatic cultivation purposes. the monitoring results also revealed that the quality of seawater in Nha Trang bay has been improved.