A multiwall carbon nanotube paste electrode (MWCNTPE) was fabricated to investigate the detailed electrochemical behavior of methacetin and achieve its sensitive electroanalytical determination. The sensitive and selective square wave anodic peak seen at +1.06 V was linearly related to methacetin concentration in the range of 0.11 to 22.3 mg L-1 [0.665 to 135 mu M]. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.032 mg L-1 [0.193 mu M] and 0.11 mg L-1 [0.665 mu M], respectively. The percentage recovery of methacetin calculated from natural lake water samples spiked at the 5.0 mu g mL(-1) [30.3 mu M] level was 94.2% with a relative standard deviation of 0.21%. The considerably high recoveries and low standard deviations were evidence for the high accuracy and precision of the recommended method. The recovery of 10.0 mu g mL(-1) [60.5 mu M] methacetin in the presence of the same concentrations of other pesticides such as benzanilide, propanil, tribenuron methyl, rimsulfuron, metsulfuron methyl and chlorsulphuron ranged from 89.2% to 98.3%. The oxidation peak of 10 mg L-1 [65.3 mu M] dopamine appeared at +0.740 V(vs. Ag/AgCl) and did not display a significant interfering effect, therefore methacetin and dopamine could be simultaneously determined.