Investigation on the toxic effects of pharmaceutical drugs namely clofibric acid (CA) and diclofenac (DCF) were studied in a common carp Cyprinus carpio at different concentrations such as 1, 10 and 100 mu g L-1 for a short-term period of 96 h under static bioassay method. At all concentrations, red blood cell (RBC), plasma sodium (Na+), potassium (K+), and glutamate oxaloacetate transaminase (GOT) levels were decreased in fish treated with CA and DCF. Contrastingly, white blood cell (WBC), plasma glucose, protein, lactate dehydrogenase (LDH) and gill Na+/K+-ATPase level were increased. However, a mixed trend was observed in hemoglobin (Hb), hematocrit (Hct), plasma chloride (Cl-), mean cellular volume (MCV), mean cellular hemoglobin (MCH), mean cellular hemoglobin concentration (MCHC) and glutamate pyruvate transaminase (GPT) levels. There was a significant (P<0.01 and P<0.05) change in all parameters measured in fish exposed to different concentrations of CA and DCF. In summary, the alterations in hematological, biochemical, ionoregulatory and enzymological parameters can be used as biomarkers in monitoring the toxicity of CA and DCF in aquatic environment. However, more detailed studies on using of specific biomarkers to monitor the human pharmaceuticals are needed. (C) 2011 Elsevier B.V. All rights reserved.