Hepatitis A virus (HAV) is single-strainded RNA virus that causes infectious hepatitis A. Detection and quantification of hepatitis A virus in Tianjin coastal seawater of Bohai Bay were carried out by conventional RT-PCR and SYBR Green real-time quantitative RT-PCR using the primers based on the conserved sequence at the VP1-VP2 genes of HAV. The nine samples were taken at Tianjin coastal seawater of Bohai Bay locating in the south of Tanggu, in summer, autumn and winter of 2007 and spring of 2008. For viral detection, seawater samples were concentrated either using a small ultrafiltration system (Millipore Pellicon Mini TFF) or a Centriprep-100 centrifugal ultrafiltration device (Millipore Centricon Plus-70). RT-PCR analysis showed that a 192 bp HAV cDNA was amplified from all nine seawater samples and the sequence identities of these cDNAs to the homologous sequence in the GenBank were between 95% and 100%. SYBR Green real-time quantitative RT-PCR analysis indicated that HAV concentration in these samples ranged from 5.35 x 10(6) to 4.51 x 10(7) virus particles/L.