Prior studies showed that albumin supplementation of the resuscitation for hypovolemic shock caused an increase in serum albumin but a fall in serum globulins; immunoglobulins were not measured. Using frozen sera, immunoglobulins (IgG, IgM, IgA, IgD) were measured in 184 severely injured patients including 40 patients prospectively randomized for supplemental steroid therapy and 46 patients prospectively randomized for supplemental albumin therapy. The remaining patients served as the control patients.Compared to normal, the control patients had a significant reduction in IgG, IgM, and IgA. This reduction was associated with a fall in total serum proteins and serum albumin concentrations. Supplemental albumin resulted in an increase in the serum albumin concentration but a reciprocal fall in the serum globulin fraction and in IgG, IgM, and IgA. The serum proteins and immunoglobulins in the steroid patients were significantly below normal but similar to that seen in the control patients. The reduction in serum proteins and immunoglobulins in the control and steroid patients paralleled the shock time (systolic pressure below 80 mm Hg) and the amount of plasma given during resuscitation. These correlations were not significant in the albumin-supplemented patients. These data indicate that albumin supplementation alters the normal immunoglobulin response to shock. These changes in the postinjury recovery period need further study.