Serologic screening for infectious disease in sentinel mice from rodent colonies is expensive and labor-intensive, often involving multiple assays for several different infectious agents. Previously, we established normal reference ranges for the protein fractions of several laboratory strains of mice by using a commercially available agarose system of protein electrophoresis. In the current study, we address protein fractionation and quantitation of acute phase proteins (APP) in mice experimentally infected with Sendai virus or mouse parvovirus. We further investigate this methodology by using samples from sentinel mice from colonies with endemic infection. All study groups showed significant increases in gamma globulins. Various other protein fractions showed mild variable changes; significant differences were not detected for individual APP. These results contrast the significant changes observed in APP and protein electrophoresis by using the standard methods of inducing inflammatory responses through injection of complete Freund adjuvant or LPS. These present data suggest that although quantitation of individual APP may not be helpful, gamma globulin levels may reflect infection in laboratory mice and provide a possible adjunct to traditional screening methods.