A sensitive square wave voltammetric method for the determination of chloramphenicol (CAP) was developed using electrochemically pretreated glassy carbon electrode (EPGCE). Electrochemical pretreatment of the electrode greatly enhanced the reduction peak current (I_p) of CAP. The electrochemical investigation of CAP was carried out by using cyclic and square wave voltammetry techniques. CAP shows an irreversible reduction peak at -0.646 V vs. Ag/AgCl at the EPGCE in 0.05 M CH₃COONa/CH₃COOH buffer of pH 5.3 using the cyclic voltammetric mode. Detailed experiments were carried out to establish the electrochemical property, the optimal pH, electrode pretreatment potential and square wave voltammetric parameters. Following optimization of the instrumental parameters and pH of buffer solutions, the peak current response for the reduction of CAP was observed showing a linear calibration curve in the concentration range of 1.0 x 10^-7 - 7.0 x 10^-5 M CAP. Over this concentration range, two good linear ranges were obtained between the voltammetric current and CAP concentration. The first was in the linear range 1.0 x 10^-7 - 5 x 10^-6 M CAP (r = 0.999) and the second in the linear range 5.00 x 10^-6 – 7.00 x 10^-5 M CAP (r = 0.999). For a series of six determinations of CAP at 1.00 x 10^-5 M and 5.00 x 10^-7 M levels relative standard deviations of 2.2 % and 3.7 %, respectively were obtained, showing an excellent reproducibility of the EPGCE. When the signal to noise ratio is 3, the detection limit was 6.0 x 10^-9 M. The experiment on the possible interfering substances showed that the electrode has excellent selectivity for the detection of CAP. The method was verified by the determination of CAP in eye drops.