The nutritional state of 12 patients with quadriplegia, secondary to spinal cord injury, was assessed by determining body composition with a multiple isotope dilution technique. For comparative purposes, similar measurements were obtained in 25 normal volunteers. The mean duration of quadriplegia was 14.8 +/- 8.5 months. All the patients were hospitalized, receiving a regular hospital diet and all were on a similar rehabilitation program. Because skeletal muscle atrophy is extensive in quadriplegics, we had expected a reduced body size, which was otherwise normal in composition, with a comparable decrease in both the body cell mass (BCM) and the extracellular mass (ECM). Instead, a body composition characteristic of malnutrition was observed in an unexpectedly large percentage (58%) of patients. In the normally nourished individual, the BCM and ECM are approximately equal in size. However, in seven of the 12 quadriplegic patients, the body composition was characteristic of malnutrition, with a BCM (13.5 +/- 1.6 kg) which was reduced relative to the ECM (28.7 +/- 1.9 kg). Their body composition was significantly (p less than 0.05) different from the body composition of both the healthy volunteers and the other five quadriplegic patients, whose body composition was normal (BCM = 22.9 +/- 1.5 kg, ECM = 28.5 +/- 1.6 kg). The nutritional state of the quadriplegic patients correlated significantly with the level of spinal cord injury and not with the duration of quadriplegia.