The present study was conducted to evaluate the bacteriological quality of water collected from tropical lake system. For this purpose, nine water sampling stations from Yamoussoukro lake system were monitored between February 2007 and April 2008 for Heterotrophic Plate Count (HPC), total coliforms and faecal coliforms (Escherichia coli). Varying levels of bacteriological contamination were recorded in all the stations. Bacterial indicator numbers (log means CFU/ mL) varied from 5.96 to 6.18 for HPC, 5.25 to 5.69 for total coliforms and 3.49 to 4.07 for E. coli. Results of this study showed that the water quality has deteriorated in Yamoussoukro lake system. In conclusion, it is important to provide sanitary monitoring program for the water.