In contrast to other types of starvation which are characterized by low CD4+ counts and increased susceptibility to infection, anorexia nervosa is not associated with an increase in infectious complications. To determine why infection risk of anorectics differs from that of other starving populations, we studied T-lymphocytes, including CD4+ and CD8+ phenotypes, in patients with anorexia nervosa, and for comparison, in dieting obese subjects. Methods: T-lymphocyte phenotypes were determined by flow cytometric analysis of monoclonal antibody-labeled cells obtained from patients with anorexia nervosa before and after successful therapy and weight gain, and in obese subjects before and after weight loss on a very-low-calorie diet. Results: Weight loss in anorectics and obese dieters was associated with normal CD4+ counts. Unexpectedly, CD8+ counts were low in anorectics, both before and after weight gain, and in obese subjects after (but not before) dieting. Discussion: Normal CD4+ counts in anorectics and obese dieters, despite marked weight loss, may explain the lack of increased infection risk in these eating-disordered patients, in contrast to other starving populations. The observation that CD8+ counts are low in anorectics with low and restored body weight and in obese patients after dieting has not been previously reported. The persistence of low CD8+ counts in anorectics even after weight gain suggests that some factors other than weight loss per se may be involved, possibly including effects due to stress, comorbid psychiatric conditions, or unidentified aspects of dysregulated pathophysiology secondary to disordered eating. © 1996 by John Wiley & Sons, Inc.