The immunoglobulin levels (IgG, IgA, IgM, IgD, and IgE) were studied in 28 Northern Thai children with protein-calorie malnutrition (PCM). Of these 14 had marasmus, 7 had marasmus-kwashiorkor, and 7 had kwashiorkor. The immunoglobulin levels were measured on admission and serially during 12 weeks of treatment leading to recovery. All immunoglobulin fractions either equalled or exceeded levels seen in well-nourished urban and rural Thai children, with or without infection. There was no difference in levels of IgG, IgM, IgA, or IgD in children with marasmus when compared with those who had marasmus-kwashiokor or kwashiorkor. IgA levels were higher in malnourished than control children and returned to normal with treatment. Eighty percent of the children with PCM had detectable IgD levels while 64% had detectable IgE levels as compared to none in the control groups. Ten additional children admitted with PCM and 10 who had recovered from PCM were immunized with intradermal typhoid antigen. Within 8 days a significant increase in typhoid H antibody appeared in the recovered group, while the malnourished group demonstrated no significant increase in H antibody titer.