Abstract: The multi-wall carbon nanotube (MWCNT) modified glassy carbon electrode was prepared by dropping 10 μL of homogeneously dispersed suspension of MWCNT in 10 g·L-1 sodium hexa-metaphosphate solution on the polished surface of a glassy carbon electrode and then it was dried under radiation of IR-lamp. In a phosphate buffer of pH 7.0,a sensitive oxidation peak given by 6-mercaptopurine (6-MP) was observed at 0.357 V (vs. Ag/AgCl) at the above mentioned modified electrode (CNT/GCE). Linear relationship between the peak current (Ip) and the concentration of 6-MP in the range of 5×10-7-1×10-4mol·L-1,with a detection limit of 5.0×10-8mol·L-1. The proposed method was used in the determination of 6-MP in simulated samples of blood serum with values of recovery in the range 98.0%-104.7%. Value of RSD′s (n=10) found at the concentration level of 1×10-5mol·L-1 of 6-MP was 4.2%.