Context: Physico-chemical factors directly affect the water quality. Biological parameters varied from pond to pond according to the water quality. Objective: To assess the physico-chemical conditions and plankton abundance in the studied ponds. Materials and Methods: The study was carried out for a period of seven months from June, 2008 to December, 2008 in six ponds of Rajshahi Metropolitan area. Surface water samples were collected once a month at 10-11 am in black plastic bottle and

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... for the estimation of different parameters. Water temperature, transparency, pH, dissolved oxygen (DO), free carbon dioxide (CO2), biological oxygen demand (BOD), nitrite nitrogen (NO2 --N), nitrite (NO2), toxic ammonia, ammonium ion (NH4 + ) and total hardness were measured. The density of plankton was also estimated. Results: The mean values of water temperature varied from 28.73 ± 3.98 (Pond 6) to 29.56 ± 4.68°C (Pond 4) and the pH varied from 7.37 ± 0.26 (Pond 6) to 8.57±0.26 (Pond 4). The DO varied 1.66 ± 1.03 (Pond 1) to 4.68 ± 0.36 mg/l (Pond 6) and the mean value of free CO2 varied from 4.29 ± 0.37 (Pond 5) to 50.91 ±19.30 mg/l (Pond 3). The total hardness was 136.79 ± 20.28 (Pond 6) to 183.14 ± 51.17 mg/l (Pond 3) with NO2 -varied from 0.003 ± 0.002 (Pond 5) to 2.08 ± 0.59 mg/l (Pond 4). The mean total phytoplankton was 28761.43 ± 2912.62 (Pond 2) to 63629.29 ± 20214.44 cells/l (Pond 4) and the mean total zooplankton was 13314.24 ± 3189.70 cells/l (Pond 5) to 18820.00 ± 932.51 cells/l (Pond 4). Conclusion: The deterioration in the physico-chemical quality and plankton population observed in this study is alarming, and periodic monitoring and preventative measures are required to save the aquatic system from eutrophication.