This pilot study examined the effects of a multimodal pain rehabilitation program on the immune function, self-reported pain, depression levels, and health behaviors of patients with chronic back pain. It also estimated the relationships between self-reported pain levels, immune function, depression, and health behaviors. Data were collected at week 1 (baseline) and at week 4 (last week of treatment program) on a convenience sample of 23 patients. In general, the patients' mean T lymphocyte proliferation levels showed a decline from baseline to week 4, while natural killer cell activity showed a slight increase in cell lysis. None of the findings were statistically significant. Failure to detect significant differences may be attributed to a small effect size due to the relatively small sample size. The depression levels dropped significantly during the treatment program (p = .001). Reported levels of pain and health behaviors did not significantly change. More research is needed to determine treatment effects on immune function as well as relationships between pain levels, immune function, depression, and health behaviors in this patient population.