Plasma beta-endorphin-like immunoreactivity (BEP-ir) and cortisol levels were measured by radioimmunoassay (RIA) in nine patients who were at least 12 months status post spinal cord injury (SCI). Plasma levels were obtained at 8:00 am and 4:00 pm to determine circadian rhythm, and on the day following administration of 1 mg dexamethasone, levels were again obtained at 8:00 am and 4:00 pm. The mean morning levels of plasma BEP-ir were significantly lower than control values for this laboratory (6.2 +/- 1.2 v 12.0 +/- 2.3 pg/mL). The morning BEP-ir values were lowest in patients who were closer to the time of injury (described by a second-order polynomial regression, R = .89; P less than .01). Mean morning cortisol levels were not significantly different from controls, but showed greater variability (mean, 15.1; range, 0.7 to 22.7 micrograms/dL v control, 15.5; range, 7 to 35). Dexamethasone suppressed cortisol secretion in all patients and BEP-ir levels in six of nine patients. Failure to detect BEP-ir suppression occurred in patients whose BEP-ir levels were less than 4.5 pg/mL and close to the minimum detection limit of the assay. Depression was present in five of nine patients as measured by the Beck Depression Inventory (BDI) and in three of nine patients as measured by the Hamilton Depression Scale (HSRD). However, the depression indices did not correlate with the neuroendocrine measures.