This study compared basal concentrations of plasma beta-endorphin/beta-lipotropin-like immunoreactivity and dexamethasone suppression of cortisol in seven chronic pain patients, seven psychiatric disorder patients, and seven normal volunteers. Pain patients and psychiatric patients showed significantly higher basal concentrations of beta-endorphin/beta-lipotropin-like immunoreactivity compared to normal volunteers. Pain patients also had significantly higher beta-endorphin/beta-lipotropin-like immunoreactivity than psychiatric patients, even though there was no significant difference in severity of depressive symptomatology as assessed by Beck and Hamilton scores. Resistance to dexamethasone occurred in 57% of pain patients. These results may indicate that biological markers for depression occur in populations of chronic pain patients, or may reflect levels of central nervous system arousal in response to stress, pain, or nonaffective phenomena.