The selenium status of 13 adult home parenteral nutrition (HPN) patients was evaluated using 12 healthy adult volunteers as controls. Patients had been maintained on HPN for a mean of 36 months and averaged 121 cm of residual small bowel. Prospective diet surveys in patients indicated a mean oral caloric intake of 902 kcal/day. The mean plasma selenium concentrations (microgram/g) were 0.044 in patients and 0.117 in controls (p less than 0.01). The erythrocyte glutathione peroxidase activities, as mumol of NADPH oxidized/g hemoglobin/min, averaged 11.01 in patients and 31.76 in controls (p less than 0.01). Four patients exhibited myalgic symptomatology suggestive of clinical selenium deficiency. No correlations could be ascertained between plasma selenium levels and glutathione peroxidase activities in either patients or controls. Additionally, in the patient group, no significant correlations could be ascertained between selenium status and oral caloric intake, residual small bowel length, symptomatology suggestive of deficiency or HPN duration. However, since sample size was not large, lack of correlations might best be considered suggestive not conclusive. The data indicate that HPN patients with small bowel resections exhibit suboptimal selenium status and may be at risk of developing clinically evident selenium deficiency. HPN patients should be prophylactically supplemented with selenium regardless of oral intake, duration of HPN, or residual length of resected small bowel.