In the present study, we purified hcbCA I and II from human cord blood erythrocytes using by Sepharose-4B-L tyrosine-sulfanilamide affinity gel chromatography. Also, it was checked the inhibition effects of ampicillin sulfate, ceftriaxone, ceftizoxime and ranitidine on hcbCA I and hcbCA II. IC50 values for ceftriaxone, ceftizoxime and ranitidine were found to be 27.l, 79.4 and 55.5 mu M for hcbCA I and of 21.0, 79.1 and 66.1 mu M for hcbCA II, respectively. According to these results, Ampicillin sulfate inhibited only hcbCAII and IC50 values of this antibiotic was found to be 56.8 mu M. All these substances were found non-competitive inhibitors. It is important to study the inhibition effects of these drugs on hcbCA I and II izoenzymes. Because, pregnant woman is take all of these substance. For this reason, these drugs should be carefully used and the dosage should be very well ordered to minimize side effects.