The present study aimed to examine the common opinion that “acute low back pain subsides early whereas chronic low back pain (LBP) is resistant to treatment”. Pain intensity in 94 LBP patients (mean age 54 years) was measured using a visual analog scale (VAS) and the change in VAS score (∆VAS, mm/day) was investigated. The initial ∆VAS (∆VAS–i) and the entire ∆VAS (∆VAS–t) were investigated. ∆VAS–i was calculated from examinations at the first and second patient visits. ∆VAS–t was calculated from examinations at the first and last patient visits. Patients were classified into an acute group, who had less than three months (≤ 3M) duration of their current LBP, and a chronic group, who had more than three months (> 3M) duration of their current LBP. Patients were also classified according to the duration of their current LBP and past history of LBP into true–acute, recurrent, and true–chronic groups. The true–acute group included those with acute onset (≤ 3M) of their current LBP, without a history of LBP. The true–chronic group included those with chronic (> 3M) onset of their current LBP, with a history of continuous LBP leading to their current LBP. The other patients were classified into the recurrent group. Every patient was initially prescribed only oral and/or topical nonsteroidal anti–inflammatory drugs (NSAIDs) regardless of the diagnosis and pain intensity. The ∆VAS–i and ∆VAS–t were significantly larger in the acute group (n=65) than in the chronic group (n=29), and significantly larger in the true–acute group (n=11) than in the true–chronic group (n=12). Our previous study demonstrated that ∆VAS–i and ∆VAS–t in acute LBP are correlated with prognosis and outcome. Acute LBP patients have pain with a large ∆VAS score that reduces rapidly, while chronic LBP patients show a relatively small ∆VAS score and are resistant to NSAIDs. Thus, the present study confirmed the common opinion.