A novel carbon nanotubes modified glassy carbon electrode was simply and conveniently fabricated. The electrochemical properties of daunomycin at the carbon nanotubes modified electrode were investigated, and two pairs of redox peaks were observed at the different potentials. Based on this, an ultrasensitive electrochemical method was proposed for the determination of daunomycin. The reduction peak current at more negative potential is linearly with the concentration of daunomycin over the range from 2 x 10(-8) to 1 X 10(-5) M, and the detection limit is 8 x 10(-9) M at 3 min open-circuit accumulation. The relative standard deviation at 2 x 10(-7) M daunomycin was about 6% (n = 10). The analysis method is demonstrated by using urine samples obtained from cancer patients following intravenous administration of daunomycin. The total analysis time was less than 10 min.