A long-term study of temperature, pH, turbidity, suspended solid, salinity, dissolved oxygen, biochemical oxygen demand and ammonia nitrogen has been performed in a port and harbour region in India for four years from December 1996 to November 2000. Marine water quality results showed no regular trend. The mean monthly values of temperature, pH, turbidity, suspended solid, salinity, dissolved oxygen, biochemical oxygen demand and ammonia nitrogen were in the range of 22.64 +/- 0.4 to 29.05 +/- 1.37 degrees C; 7.65 +/- 0.04 to 7.81 +/- 0.13; 28.8 +/- 14.7 to 64.2 +/- 32.0 NTU; 283.5 +/- 81.8 to 356.0 +/- 159.7 mg/L; 29.78 +/- 7.18 to 29.78 +/- 1.04 ppt; 4.67 +/- 0.50 to 6.01 +/- 1.02 mg/L; 5.41 +/- 1.92 to 7.56 +/- 2.1 mg/L; and 0.25 +/- 0.07 to 0.63 +/- 0.49 mg/L, respectively. The results of correlation analysis showed that biochemical oxygen demand (BOD) was inversely correlated dissolved oxygen (DO) and poorly correlated with all other parameters. Turbidity and suspended solid were moderately correlated with each other while salinity was moderately correlated with other water quality parameters. In factor analysis, four factors were drawn out of the eight variables, which represented 74% of the variance of the original data. Factor I was related to suspended solid and turbidity. Factor II represented mainly temperature and DO showing inverse relation between these two. Factor III implied the degree of pollution at any monitoring station. Factor IV included pH and salinity. It could be concluded that the factor model represented almost all the variables.