The present work is concerned with the determination of blood parameters, enzyme levels, blood chemistry and pesticide residues in the blood samples from different areas of Karachi in comparison with unexposed persons (i.e., control). Total 45 persons (exposed to pesticides) were taken in this study to assay the pesticides residues in their blood and also observed the morphological and chemical changes in the blood of affected persons. From 45 persons, only 20 persons were found positive and included in the study. Out of ten (10) standard pesticides five differentpesticides were identified in the blood of exposed persons such as cypermethrin, deltamethrin, polytrin-C, malathion and permethrin. The other standard pesticides such as DDE, DDT, match, diazinon and monocrotophos were not detected. In addition blood samples were also collected from ten (10) normal persons (not exposed to pesticides) for the determination of blood parameters, enzymes levels and blood chemistry. Regarding blood parameters approximately all the blood samples had significant variations i.e., (increase or decrease level) possibly due to the cumulative effect of pesticide residues e.g., Majid a young male aged 25 years had been exposed to pesticides for long time and therefore his TLC and platelet counts were found high in addition to low levels of RBC count, Hb, Hct and MCH which probably due to the excessive secretion of enzymes. Similarly, Ghulam Hussain another young male person aged only 08 years had low levels of RBC, Hb, Hct, platelet, MCV and MCH, which may be due to toxic effects of pesticides. In differential leukocyte count (DLC), granulocyte count was found in lower limits in 40 samples and showed normal limits in 05 samples. Lymphocyte count was xi found high in 31 samples. Low limit of lymphocyte was not found in any person. Similarly, monocyte count was found in high limits in 38 samples. Low monocyte count was not noted in any sample and the rest of the samples had normal limits of monocyte. Positive effects of pesticide residues were also observed on the enzyme levels. Regarding enzyme levels GPT, ALP, and ɣ - GT had higher levels in maximum number of samples. Cholinesterase was found high in 6 samples out of 45 samples and the highest was found in case of Farhan and Abdul Rahmanwhere as low limit of cholinesterase was noted in 15 samples out of total samples which may due to prolonged exposure of pesticides. GPT was found in high limits in all the samples. Also ɣ - GT and ALP found high in all the samples. Effect of pesticide residues were also observed on the blood chemistry. Regarding total bilirubin only one sample showed normal limit. The rest of the samples had raised total bilirubin and the highest was found in Javed a young male person aged 12 years. Similarly, in case of bilirubin direct all the blood samples showed increased level. The standard chromatograms of 10 different pesticides such as match, cypermethrin, deltamethrin, polytrin-C, diazinon, DDE, monocrotophos, DDT, malathion and permethrin were prepared on HPLC and their retention time (RT) was noted. Calculation was done for the quantity of pesticides residues from the peaks of chromatograms. Regarding pesticide residues, out of total 45 samples, only 20 persons were found positive for residues. The quantity of pesticide was determined by comparing xii the peak area of the standard pesticide with the sample peaks. After analysis, it was found that out of 20 samples deltamethrin and cypermethrin were found in noticeable amount in 6 samples. Also polytrin-C, malathion and permethrin were found in 2, 1 and 5 samples respectively. The pesticides such as match, diazinon, DDT and monocrotophoswere not detected in any sample.