Abstract
1. The effect of 1.5, 2.0 and 5.0 ppm methidation was studied on the ASAT, ALAT, LDH and AChE enzymes, as well as the blood sugar and adrenaline levels in carp. 2. According to our studies methidation implies a potential hazard on the normal biochemical processes of fishes: causing tissue necrosis indicated by the increase ASAT, ALAT and LDH activities, inducing continual stress effect reflected by the increased blood sugar and adrenaline levels, inhibiting AChE activity in the various organs, the consequence under acute effects being fish kill.