To investigate the effects of acupuncture on perceived pain, mood disturbances and medical expenses related to low back pain (LBP), an intervention study was performed among 72 employees of a steel company, 70 males and 2 females, aged 53.1±7.1 (mean±SD) yr, with LBP. They received acupuncture treatment once a week for 8 wk (from October to December 1998) by licensed acupuncturists, adopting a new hypothesis of the Meridian test. Perceived pain scale, and Profile of Mood States (POMS) were administered. Past and present histories of employees' visits to hospitals and their medical expenses for LBP were surveyed from receipts obtained from the subjects' branch factory and from receipts from another nearby branch factory (control) during the period from April 1998 to March 1999. After 8 wk of treatment, patients with LBP reported diminished pain (p<0.01). POMS showed a significant decrease in the total mood disturbance score (p<0.001). The number of visits to conventional hospitals (12.1±8.0 vs. 0.8±0.8 per month, p<0.05) and standardized medical expenses for LBP (100.1±89.6 vs. 7.3±6.9 per month, p<0.05) after acupuncture intervention (November 1998 to March 1999) were significantly decreased as compared with those before intervention (April 1998 to October 1998). In contrast, such decreases were not observed in employees from the control branch factory. It is suggested that acupuncture can reduce medical expenses for LBP through improvement in mood and pain.