To describe the design of a randomized controlled trial (RCT), including a cost-effectiveness analysis, comparing high-intensity and low-intensity back schools with usual care in occupational health care. RCT and cost-effectiveness analysis. Employees sick-listed for a period of 3 to 6 weeks because of nonspecific low back pain. Interventions High-intensity back school treatment consists of a training program based on the principles of cognitive-behavioral therapy. Low-intensity back school treatment is comparable to the original Swedish Back School. Usual care is provided by the occupational physician according to the Dutch guidelines for the occupational health treatment of patients with low back pain. Primary outcome measures are return to work, pain intensity, functional status, and general improvement. Secondary outcome measures are kinesiophobia and pain coping. The cost-effectiveness analysis includes the direct and indirect costs. The outcome measures are assessed before randomization and 3, 6, and 12 months after randomization. RCTs of different methodological quality have been conducted to examine the effectiveness of back schools in occupational health care. The large variation in type, content, and intensity of back schools has led to conflicting evidence. Therefore, 2 different forms of back schools are compared. Moreover, this is the first RCT to include a cost-effectiveness analysis comparing low-intensity and high-intensity back schools with usual care in occupational health care.