The influence of Penncozeb [Mangan-zinc ethylenediamine-bisdithicarbamate], Dithane, [Manganese etylenebisdithiocarbamate], Cupravit [Cuper oksichloride]. Bayleton [1-(4-chlorophenoxy)-3.3-dimethyl-1-(1H-1.2.4-Thiazol-1-yl)-2.2-butanon], Baythroid [Cyano-(4 fluoro-3-phenoxyphenyl)-methyl-3-(2.2-dichloroethyl-2.2 metyl-cyclopropancarboxylate], Mavrik [cyano-3-phenoxybenzyl N-(2-chloro-trifluoro-p-tolyl], Talstar [2-methyl biphenyl-3-ylmethyl(z)-(IRS,3RS)-3-(2-chloro-3.3.3-triflouroprop-1-enyl)=Dimethylcyclo propenecarboxyate], Endosulfan [126.96.36.199.10.10-hekzachloro- 1.5.5a.6.9.9a-hekzahydro-6.9-methano-2.3.4-benzole dioxi atehiepin 3-oxide] has wen investigated on human erythrocyt carbonic anhydrase isozymes (HCA-I, HCA-II) Ind bovine erythrocyte carbonic anhydrase (BCA) in vitro. Among the chemicals; Baythroid, Talstar, Mavrik were determined to have inhibition effect, on bovine CA and human CA isoenzymes. Dithane had effect of inhibition only on BCA. The I-50 values of chemicals caused inhibition were determined by means of activity percentage [I] diagrams. The values were 2.77x10(-3) M. 3.8x10(-3) M, 1.56x10(-2) M, 2.36x10(-2) M for BCA, respectively. The values of same chemicals except dithane were 1.67x10(-3) M, 4.64x10(-3) M, 3.9x10(-3) M for HCA-I, and 3.16x10(-2) M, 2.81x10(-3) M. 1.04x10(-2) M for HCA-II, respectively. On the other hand, Changes occurred in stock concentration of chemicals showed activator effect were calculated. According to the results reached, 10(-2) M cupravit, 4.17x10(-2) M endosulfan and 10(-2) M bayleton in stock concentration activated on both BCA and HCA-II at different levels. The values activation increases of these chemicals on BCA were 29.90, 46.40, 43.70%, and 67.11, 57.23, 31.88% for HCA-II, respectively. Cupravit and bayleton which activated to BCA and HCA-II were ineffective on HCA-I. Values of endosulfan was determined to be 114.40%. Penncozeb was recorded ineffective for all isozymes.