We asked 78 chronic low back pain patients to report on their usual pain intensity, and on the lifestyle changes caused by their pain, on a horizontally-oriented visual analogue scale (VAS). Also, the usual and the current pain intensities were examined on a vertical VAS. Statistical analysis showed normal distribution of data in the measurement of usual pain on the horizontal VAS, but no homogeneous distribution on the vertical VAS. Therefore, in the measurement of chronic low back pain VAS should be used horizontally rather than vertically, because of higher sensitivity. The intensity of usual pain was significantly correlated with the degree of lifestyle change. No correlation was found between current and usual pain. There was no significant difference in the failure rate between the vertical and horizontal VAS. Also, there was no reduction of the failure rate by giving additional oral explanations in the use of the scale to the patient. Owing to a negative influence in distribution of rates and an increase in the failure rate, complex questions should be avoided. A short written introduction to the scale is sufficient, and oral explanations are not essential.