The major objective of this research is to evaluate the efficacy of two qualitatively different treatments of hospitalized anorexia nervosa patients: behavior modification and cyproheptadine HCL (Periactin). After one week pretreatment period during which the patients will be carefully assessed psychiatrically and medically, random allocation to one of the four treatments will be made: a) Periactin and behavior modification b) Periactin and no behavior modification c) placebo and behavior modification and d) placebo and no behavior modification. After random assignment the patients will be followed for 35 days and assessed periodically.