To assess the effects of physician's advice on non-specific acute low back pain (ALBP) in Japanese workers, existing data from a prospective, epidemiological study of Japanese workers were analyzed. Among workers who had had low back strain during the past year at baseline and responded to the 1-yr follow-up survey (n=475), those who obtained medical care (n=255) and received advice either to rest (n=68 for the rest group) or to stay active (n=32 for the active group) were examined. The rest group seemed to have a higher risk of ALBP than the active group after adjusting for age, gender, history of low back strain, type of physical activity at work, and severity of LBP during the past month at baseline (adjusted OR for the rest group vs. the active group: 3.65, 95%CI: 0.96-13.8). Compared to the active group, low back strain was more likely to occur repeatedly and to become chronic in the rest group. These findings suggest that advice to rest may not be better than advice to stay active for preventing future episodes of ALBP in Japanese workers, which is consistent with previous studies or guidelines for the management of ALBP in Western countries.