The kinetic parameters of inhibition of camel retinal acetylcholinesterase (AChE) activity by cycloheximide (CH) were investigated. For the control system, the Michaelis-Menten constant (K(m)) for the hydrolysis of acetylthiocholine iodide was found to be 0.076 mmol/L and the Vmax was 0.547 mumol/min per mg protein. In contrast, these parameters were decreased in the CH-treated systems. Dixon and Lineweaver-Burk plots, and their secondary replots, indicated that the inhibition was of the linear mixed type, which seems to be a combination of partial competitive and pure noncompetitive inhibition. The values of K'i(slope) and KI(intercept) were estimated to be 3.50 and 5.68 mmol/L, respectively. Ki was greater than K'i, indicating that CH has a greater binding affinity for the peripheral site than the active site.