This investigation examined surface electromyography as an additional tool in the comprehensive clinical evaluation of patients with chronic low back pain (CLBP). Electromyographic signals from electrodes placed in the lumbar area of 30 CLBP patients and 30 non-pain control subjects were compared. Patients and controls were matched for age, gender, and body mass index. Paired t test showed a statistically significant difference between the two groups. The muscle activity mean values were threefold higher in CLBP patients than in controls (P < 0.00001) in the static testing, and twofold higher in CLBP patients than in controls (P < 0.00001) in the dynamic testing. Our findings indicate that surface electromyography assessment of the paraspinal muscle activity may be a useful objective diagnostic tool in the comprehensive evaluation of CLBP.